The cover image was created by the transcriber and is placed in the public domain.

Copyright, Ewing Galloway

The Majestic, Largest Steamship in the World

Popular Science Library

EDITOR-IN-CHIEF

GARRETT P. SERVISS

AUTHORS

• WILLIAM J. MILLER
• HIPPOLYTE GRUENER
• A. RUSSELL BOND
• D. W. HERING
• LOOMIS HAVEMEYER
• ERNEST G. MARTIN
• ARTHUR SELWYN-BROWN
• ROBERT CHENAULT GIVLER
• ERNEST INGERSOLL
• WILFRED MASON BARTON
• WILLIAM B. SCOTT
• ERNEST J. STREUBEL
• NORMAN TAYLOR
• DAVID TODD
• CHARLES FITZHUGH TALMAN
• ROBIN BEACH

ARRANGED IN SIXTEEN VOLUMES WITH A HISTORY OF SCIENCE, GLOSSARIES AND A GENERAL INDEX

ILLUSTRATED

VOLUME SIXTEEN

P. F. COLLIER & SON COMPANY

NEW YORK

Copyright 1922

By P. F. Collier & Son Company

MANUFACTURED IN U. S. A.

HOW TO USE THE POPULAR SCIENCE LIBRARY
BY
GARRETT P. SERVISS
HISTORY OF SCIENCE
BY
ARTHUR SELWYN-BROWN
GENERAL INDEX

P. F. COLLIER & SON COMPANY
NEW YORK

PREFACE

The final or Index volume of the Popular Science Library not only increases the value of this great set, but actually multiplies it. Volume XVI is in three parts: First, the editor, Garrett Serviss, in "How to Use the Popular Science Library," describes the way the reader may enjoy and profit most from its store of scientific knowledge in connection with his everyday experiences. Then follows Arthur Selwyn-Brown's "History of Science," an excellent foundation for the study of man's achievements in his struggle to understand and turn to his own use the forces of nature. Here is a concise record of progress from the earliest times until now—discoveries and inventions past, present, and about to come.

The third part of Volume XVI occupies nearly half the book. It is the General Index, which is as complete and as practical as it is possible for an index to be. Here, then, we have sixteen volumes on science, every work agreeable to read, every work complete in itself, and all of them, including the Index, prepared by specialists, each of whom has already gained distinction in the field he covers. The Index binds the collection into a consistent whole, making every bit of knowledge in the sixteen books available to reader or student without delay.

The style employed in the Index is a standard for such material. Volume numbers are represented by the Roman numerals, i, ii, iii, iv, v, vi, vii, viii, ix, x, xi, xii, xiii, xiv, xv, xvi. Pages are indicated by figures. All topics and subtopics are arranged alphabetically.

When you read or study the Popular Science Library, keep the Index volume at hand whenever it is convenient. It will add greatly to your interest and give you a depth of insight into these matters if you can compare one author's opinions and descriptions with those of another. If you are consulting the Library as a reference collection for information on particular topics, the Index will give you volume and page for every bit of text on the subject you are considering.

The Popular Science Library is unique in the number and standing of its authors and in the care that has been taken to make it the easiest as well as the most engrossing of all scientific collections for the reader or student to use.

CONTENTS

LIST OF ILLUSTRATIONS

HOW TO USE THE POPULAR SCIENCE LIBRARY

This series of books is written for all the people and not for specialists only, though it is the work of specialists who know how to explain their subjects clearly and interestingly, without unnecessary technicalities and with keen appreciation of the popular and constantly increasing desire for scientific knowledge.

The supreme importance of science in the wonderful age in which our lot has been cast was demonstrated with overwhelming force of conviction by the events of the World War. If, as certain persons assert, science may be accused of having rendered war more destructive and terrible, yet, on the other hand, no one can deny that it was science that saved the world from sliding backward into an age of despotism.

The true importance of science for everybody arises from its rapidly increasing service in the development of human industry in all its forms, for industry is the mother of democracy.

Said Gabriel Lippman, the French physicist, inventor of color photography, who died in the summer of 1921: "For thousands of years science progressed by groping and feeling its way, and coincidentally industry got slowly on by guesswork; but within the last century science has developed more than during all preceding time, while industry has sprung upon its feet and begun to march with the strides of a giant."

Notwithstanding its immense importance and the vast extent and complication of its application in modern times, science is not really difficult for any person of ordinary school education and of good natural intelligence to comprehend, provided it is presented in a clear, plain, common sense manner, in popular language with illustrations drawn from everyday life and experience. The much talked-of methods of science are, after all, nothing more than the methods of common sense, applied with systematic care by minds disciplined to a high degree of efficiency. And, in fact, the only practical difference between the mind of a trained scientist and that of any other intelligent person is that the scientist has acquired a way or habit of looking at and thinking about things and events, which enables him to get at their inmost nature and meaning more swiftly and accurately than he could do if he went to work in a haphazard manner as, in truth, his forerunners of the earlier centuries were obliged to do. The pioneer must always work by rule of thumb, but when he has exploited his field he knows better ways.

Each branch of science has its own particular methods, but it is not necessary for the average reader to study these special methods in order to become able to grasp the facts and principles that have been developed by them. The results are all thrown into a common store—or should be if science is to attain its utmost usefulness to humanity—and from the common store the great public, the people at large, should be enabled freely to draw. The object of this series of books is to form such a store of science for the people.

It may encourage those who look with some degree of timidity upon the task of trying to understand the great discoveries and achievements of modern science to know that even the ablest scientists, leaders in their own particular branches, do not pretend, or attempt, to grasp the special methods or the technicalities of any division of science except that one in which their own work is done. They stand, with regard to other branches, practically on the same footing with the unscientific reader, having over him only such possible advantages as their special training in clear thinking and in the intense application of the mental powers may give them.

Besides, science is really the most interesting thing in the world—outside of men and women—and they would be less interesting, even to themselves, if science had not transformed their lives as well as their surroundings. If one of Voltaire's favorite messengers from some other, wiser world had visited our earth a few hundred years ago, or even only one hundred, and should now repeat his call, he would be amazed, and no doubt delighted, by the changes in every feature of life and society which he would find that science had brought about, as if by magic, during the interval between his visits. He would be likely to exclaim: "Some great teacher and trainer from a more enlightened part of the universe must have been here since I saw this world before. What a marvelous new spirit he has imparted to these creatures. Through him they have become more masterful and more like sons of God."

See if you can find a single detail of your daily life that is not affected by science, or upon which science does not throw new light. It is fascinating to trace out the scientific relations of the simplest things that surround us, or the most ordinary occurrences and incidents.

Start with your first awakening in the morning, and you will perceive that there is not a thing that you see, or that in any way attracts your attention, that is not touched and illuminated by science, and often in the most unexpected and delightful ways. It is by considering these things that one may best perceive how to use the volumes of this little library. As you open your eyes in the morning you see a bright glow through the window curtain, then you know that the sun has risen.

But stop a moment. What does that mean—"the sun has risen"? The sun has not "risen" at all. But, one of the greatest facts of the science of astronomy is illustrated before your eyes—a fact that it took mankind thousands of years to find out. You are standing in the astronomer's shoes now, if you choose to wear them. This is a part of his field of science. It took him a long time to convince the world that the "rising" of the sun in the east next morning after its "setting" in the west really means that the globular earth has turned half way over during the night. If this seems simple to you now, it seemed very hard to comprehend to our remote ancestors, who, though reasoning men like ourselves, had not learned as much about the relativity of motion as we now know, though even we may be puzzled by some of the consequences that Einstein has drawn from it. And a hundred other things that astronomy has discovered about the sun and the other suns, called stars, and the other worlds, called planets, immediately rush to your mind, and you turn to the volume on astronomy to read about them.

But this is only a beginning of the string of everyday incidents that are rendered curiously interesting as soon as their scientific relations and meanings become evident to you. Science is right at your elbow to raise questions and to answer them the moment you step out of bed, and your mind begins to work.

As you throw open the window to see what kind of a day it is going to be, whether fair, or cloudy, or rainy, cool or warm, you draw your conclusions from the appearance of sky and air, but in doing that you are entering another field covered by another branch of science and included in our little library—meteorology, or the realm of the air—and you may be sure that the correctness of the conclusions that you draw from the aspect of the clouds and the feeling of the air will be greatly increased, not only in certainty, but also in interest, if you read what the students of this subject have learned about the laws and the mysteries of the rains, clouds, cyclones, barometric pressures, great winds and genial breezes, great storms and little storms; in short, the whole wonderful science of the atmosphere, that invisible, yet powerful kingdom of the air, which we are just beginning to annex to our world of activities without regard to what its natural occupants, the birds, think of such an invasion.

Now you leave the window to begin making your morning ablutions. You turn on a faucet and take a drink, or plunge hands and face into the refreshing liquid, so cool, lively, and invigorating. But a bird or any four-footed animal may find just as keen physical enjoyment in the touch and taste of the water as you do. You, however, because you are a thinking being, possess a source of enjoyment from the touch and appearance of the water that is not open to those humbler creatures, and that source of enjoyment springs from the principles and facts of another branch of science which the mere sight of the running water may call to mind if you have caught the spirit of these books—the science of chemistry, whose early history is filled with that irresistible kind of romance that pertains to the search for Eldorado, or the strivings of the human spirit after the powers of magic; for the realm of chemistry was once a kind of semi-scientific dreamland, wherein the "alchemists" delved at the same time for the "philosopher's stone" which was to turn base metal into gold, and for the wand of the magician which would give to its possessor the boundless gratifications of a Faust. Water is no mystery to the lower animals, but it is a great mystery even yet to the highest ones—ourselves—because we have been enabled to analyze it. You cannot look at it pouring from the faucet, and sparkling into bubbles, without recalling the fact that it is composed of two invisible, silent gases, and that chemistry tells us not only how to make the water disappear by taking those gases apart, but also how to form new water by making the two gases combine. The mystery is—why should this be so? It is a captivating question, and the business of the book on chemistry is to give you all possible light on the solution of that question, and others of a like nature. You will find, too, that the very latest chemistry has, strangely enough, discovered a sort of justification for the extravagant expectations of the ancient alchemists, by finding a way in which one substance may actually change, or be changed, into another, different substance—one "element" taking the form of another "element"—and also by getting clues to the existence of marvelous locked-up energies in matter, the release of which would give man control over powers that could properly be called "magical."

After finishing your toilet, with all the suggestions and remembrances of chemical science that it has produced, you start to quicken the circulation of your blood by catching up a pair of dumb-bells, or Indian clubs, or by pulling elastic cords, or banging a leather ball with your fists, as if you meant to go in for the championship of the world. Now, what taught you the value of such exercises? You are still on the ground of science, and you are practically demonstrating the principles of another of its branches—the science of health, or hygiene, which is a part of the subject of medicine, taken in its broadest signification, for, as the volume on that subject will assure you, the greatest service that this science can render to mankind is in teaching us the laws of our physical existence, and indicating, directly or indirectly, how all the functions of the body may be kept in the best working order by proper attention and exercise. You will find such things pointed out in the several sciences that deal with the body, such as physiology and medicine.

While you are making the leather ball strike the ceiling with resounding whacks, your dog, excited by the inspiring noise, bursts into the room, and interrupts your exercise with his enthusiastic morning greetings, expressed as energetically by his wagging tail as by his joyous barks and licks, all anticipatory of a lively morning run. He brings immediately into your mind the thought of still another division of science—zoölogy—to which you will devote many pleasant half-hours of reading, for it is full of most entertaining matter, as well as of matter calculated to awaken profound and useful thought concerning the relations of the many different members of the animal world to one another, and especially to their head and chief, man, to whom the supervision of the whole was, according to the Bible story, originally committed. Familiar as your dog may be to you, there are a hundred particulars of his family relationships, his descent from wild ancestors, etc., which can only become known to you through the studies that have been devoted to the science of zoölogy by curious-minded investigators from the times of Aristotle and Pliny down to our own day, when we have seen an ex-President of the United States wandering adventurously through some of the remotest portions of the inhabited globe, seeking fresh knowledge of, and personal acquaintance with, the rarer kinds of wild animals, and hunting down in their native wilds great beasts which the Cæsars used to admire from the security of the imperial seat, high above the bloody sands of the Roman arenas. And this modern ruler, after having laid down the political power intrusted to him by fellow citizens, found no occupation so attractive as that of adding something to the growing stores of science.

Painting, Chas. R. Knight. (American Museum of Natural History)

THE LITTLE EOHIPPUS. FROM WHICH THE MODERN HORSE DEVELOPED

ORNITHOLESTES—PREHISTORIC ANIMAL OF AMERICA

Photo, Metropolitan Museum

HUNTSMAN. HORSE AND HUNTING DOG OF LONG AGO

From an ancient Cretan fresco

Next, your stomach, awakened to its wants and needs by the restored circulation resulting from your lively exercises, reminds you of what will be at the same time a pleasure and a means of sustained strength for body and mind, your breakfast. Breakfast properly comes under the supervision of the science of physiology. It is also suggestive of mechanics and physics, since it has to do with the stoking of the furnace that keeps the bodily engine up to its work. Here you are face to face with a branch of science which you could no more safely neglect than an engineer or a fireman could neglect to learn the elements and principles underlying his critically important occupation. One of the first sciences to be systematically developed was that of man's body, including its structure, or anatomy, and its functioning, or internal action, physiology. You will find that correct ideas on these subjects were slow in being developed, yet even in the most ancient times men were shrewd and wise enough to understand the importance of knowing something about their own bodies, in order to be able to take proper care of them, and to deal with wounds and sickness.

It was an old saying that "the proper study of mankind is man." But that is a study which has two main branches. The first covers the subjects of physiology, anatomy, medicine, etc., while the second relates to that even more intimate part of ourselves which has ever been a fascinating mystery, and which we call the mind, or sometimes the soul. This is the theme of the science of psychology, whose name comes from that delicate, inscrutable spirit, Psyche, the Soul, which plays like a flitting sunbeam through the magical atmosphere of Greek mythology. Now, this subtle and exquisite science, often more poetic and mystic than scientific in its original character, presents itself in its more sober and practical dress to you as soon as, having finished your breakfast and prepared your bodily energies for the day's work, you begin to meditate on the problems of the day opening before you.

When you went to bed, perhaps your mind was agitated by some important matter of business through whose intricacies you could not clearly see your way. You turned and tossed on your pillow, and stated and restated the facts and arguments and lines of reasoning, but all the while they became more obscure and entangled until at last, in sheer exhaustion, you fell into a troubled sleep. But this morning, to your immense surprise and gratification, without any effort on your part, and while you are occupied with other things—putting on your clothes, hitting the ball, playing with the dog, eating your bacon and eggs, or what not—suddenly the elusive clue or solution, so vainly sought the night before, presents itself plain before you. In an instant, in the twinkling of an eye, the troublesome problem is solved, as easily and naturally as water runs down hill, and you are provoked at yourself for having been so dull and stupid as not to see it all before. But not so fast! You were stupid, to be sure, but it was not your mind's fault as you are now disposed to think, but the trouble lay in your physical fatigue. You were driving your brain too long without refreshment, and it became like an engine whose oil cups are empty. It could not receive and report the impressions of thought.

Now this kind of experience comes many times to many men and women, and it is the purpose of the book on psychology in this series to make everybody acquainted with the laws of the working of our minds through our brains. Yet, how many of those who are frequently puzzled by such things are aware that there is a branch of science, one of the most captivatingly interesting of all, devoted especially to this subject? By studying the volume on psychology you will get light on just such things as so greatly puzzled you, and haunted you, before the solution of your problem unexpectedly rose up, as it were, and stood plain before you on the breakfast table, after having for twenty-four hours resisted your utmost efforts to master it, or even to get an effective hold upon it. It is unnecessary to speak of the immense importance to all human beings of a knowledge of the laws governing the manifestations of the mind, by taking advantage of which they may get the most out of themselves with the least loss of time and expenditure of effort.

Let us keep on further along the wonderful road of science on which your feet begin almost unknowingly to tread from the moment of your awakening, and which they follow, often just as unconsciously, until you fall asleep at the close of another day; while, as we have just seen, even when we are asleep our minds are not altogether inactive, and may even secretly disentangle the puzzles of the day while our tired brains are restoring themselves with slumber. Perhaps you live in the suburbs of a city, or far from the business center, and have to take a considerable journey from your house to your place of work or business. Maybe you go by automobile, or by street car, or by a trolley route, or take a commuters' train. In any event, whether you drive your own car, or ride in one drawn by a motor or a locomotive engine, you are brought face to face with the science of physics, including, of course, not only mechanics, but also, in our own day, electricity and magnetism. If you glance at a steam locomotive, puffing and blowing, and then at a smooth, silent electric motor drawing a long train, and then at a swift automobile winding and turning with serpentine agility through crowds of slow horse-drawn vehicles—in all cases your memory must recall the long, hard road by which these things were brought about, and you must be lacking in intelligent curiosity if you do not resolve to know for yourself, not only the history of these triumphs of human invention, but the principles of action upon which they depend. If you have a car, it would be a good thing to drive it yourself and learn to take care of its machinery yourself, for thus you would go far toward mastering the elementary principles of the science of mechanics, which has done more than all other things combined to transform the face of the world we live in. You cannot, of course, acquire all this knowledge by practical experience, but by putting together what you observe with what you read in the volumes devoted to mechanics, physics, chemistry, electricity, etc., you will find that every day is a school day for you in which you have learned something new, useful, and interesting, and something, moreover, which every wide-awake person in this wide-awake age ought necessarily to know, and can know by pursuing such a course as that just suggested. Your morning's ride to work will be transformed into a delightful intellectual experience if you prepare yourself by a little daily reading to understand the construction and manner of working of all the machines, engines, and mechanisms presented on every side to your inspection.

But machinery is not everything in life. Suppose that as you ride along your eye is caught by the great beauty of the flower gardens by the roadside, their blossoms bright in the morning sunshine and sparkling with the yet undried dew, as if sprinkled with diamonds. Perhaps your attention may never before have happened to be called so strongly to these objects, and possibly you have hitherto remained almost unacquainted with the names and peculiarities of some of the most common plants and flowers. But this morning, for some accidental reason, which may have a psychological origin, you are particularly charmed with the brilliant sight, and you resolve that you will be no longer ignorant of what could, manifestly, give you so much pleasure, besides being of unquestionable usefulness. When you return home you will take up the volume on botany, and it may lead you into a realm of mental delight previously unknown to you.

If it is the springtime, you may be interested by the sight of a tall, graceful tree, as lofty as a pine, and as straight in trunk, with many exquisite blossoms hanging from the pendulous stems on its great limbs, fifty or more feet above the ground, as if it were a flower garden in the air for the special delectation of the birds. Having never heard of a flowering tree outside the tropics, you feel a keen desire to know what this one is, and thus a way of introduction, founded on keen, personal interest, is opened for you to the science of botany. And few persons can take a ride, or a walk, anywhere in city or country or park, without having attention attracted by some unknown flower or plant, or tree, and without becoming aware how much pleasure is lost, and how much useful knowledge missed, by lack of the easily acquired knowledge of these things, which anybody can have by giving to it only that amount of time which would otherwise be wasted almost as completely as if the eyes were kept closed and the mind dismissed from its home in the brain. More mysterious, and not less fascinating than flowers and trees, are the birds and insects that flit by on their own errands. To explain them you have the volume on zoölogy, the science of animal life. Botany and zoölogy together go far to revolutionize the ordinary man's ideas about the attractiveness of outdoor life.

For the cultivator of the soil, whether farmer, gardener, or fruit grower, botany, of course, is the queen of sciences—though he may not safely remain ignorant of the others mentioned, which form a brilliant court for his queen. In no direction has science lately proved itself so indispensable as in the application of botanical knowledge to the improvement of agricultural operations of all kinds. In France, always one of the richest of lands in this respect, the government has since the war made special provisions for placing instruction in botany and plant physiology, and the results of all advances in the science of the vegetable kingdom, before the pupils of the primary as well as those of the secondary and higher schools. Botanical reading and study are encouraged in every possible way. One of the most significant propositions for the extension of this educational reform consists in the suggestion that the schools in the country districts give much more attention to the various branches of botanical knowledge than the city schools do, for the purpose not only of supplying instruction that will be of fundamental practical use to the young people who grow up on the land and are to make its cultivation their life's occupation, but also of stimulating a love of the country for itself, its scenes, its atmosphere, its society, its amusements, and its simple, beautiful, and healthful ways of life.

As your train, or car, rushes through a rock cut where the roadway has been carried, without change of level or grade, through the round back of a hill, you may happen to see on the side walls of the excavation curious striations, or cross checkings, of the rock surface, or alternate strata, or layers, of varying color and texture; some composed of smooth-faced stone, of a dark, uniform color, and others of coarse granular masses of variegated hue, some of whose particles flash like microscopic mirrors in the glancing sunlight that grazes the top of the cut. Here, then, you are plunged into the wonder world of the geologist and the mineralogist, the subject of one of the most interesting of our volumes. That man must indeed be dull of intellect who does not feel a thrill of interest at the sight of these signs and inscriptions, written by the ancient hand of nature in the rocks, and telling, in language far more easily decipherable than the hieroglyphics of Egypt, the story of the gradual growth of this round planet on whose surface we are confined, like flies or ants, as it rotates and revolves in empty space, circling with us around a star, ninety-three million miles away, called the sun, which saw the birth of our world and has ever since kept it warmed and lighted with its rays.

In those layers of rock in the railway cut you see the leaves of the book of geology, infinitely older than the oldest scripture from man's hands, and relating things that occurred in those far-off nights and mornings of time that flitted over the globe ages before the human stem had set off from the trunk of terrestrial life. These geologic pages speak of occurrences in the building of the world that happened millions of years ago, and millions of years apart, though they have left marks and vestiges that the eye can discern as easily as if they had been the work of yesterday. No observant person can ride twenty miles through the country, especially in a hilly region, without having the fundamental facts of geology continually before him, and all that he needs in order to comprehend these things is a little preparatory reading, accompanied and followed by intelligent thought and observation. Anybody to whom all rocks look alike, and all hills the same, needs a little awakening of the mind. He is one of the persons had in view when this series was conceived and written, and he has no occasion to feel in the slightest degree offended by such a statement, for the simple fact that probably ninety-nine one-hundredths of his fellow citizens, and they among the best in the community, are just as unfamiliar with the plainest facts of geology as he is. Geology is not a difficult science to master in its main outlines, and there are few more fascinating when once its drift is caught. Even the beginner in the reading of the volume on geology, by seizing such chances of observation as every ride or walk affords, may in a very short time acquire the ability to read the history of a landscape from its face, to recognize the work of the glaciers in the great Age of Ice, to see where ancient streams flowed, or where molten rock has gushed up through the surface layers of the earth's crust, and even to recognize on sight some of the fossils, which are under everybody's feet in some parts of the country, and which still retain the forms of animals some of which were among the primal inhabitants of the earth, whose lines have died out, while others, though their individual lives expired tens or hundreds of millions of years ago, bear in their fossilized forms a close resemblance to modern relatives and descendants whose generations still flourish in the living world in this twentieth century of man's latest historic era.

Presently, turning from the attractions of the outdoor world, which seem just as entrancing the hundredth time you look upon them as they did the first time, particularly if you have cultivated the habit not merely of noticing but of thinking and reading about them, you take up the morning newspaper, in which most of your companions of the car are already deeply buried, and amid the political news, the personal gossip, the inevitable exploitation of the deeds of criminals, the foreign intelligence, and the social gossip that falls under your eyes, your attention is caught (this is an actual happening of not long ago) by the headline: "John Daniel, the orang-utan, is dead." This sounds odd. There has been no animal's obituary in the papers since Barnum lost his biggest elephant, and bequeathed its skeleton to science. You read further and find an interview with a professor about the human relationships, or apparent relationships, of the anthropoid apes, of whom "John Daniel" would probably have been the acknowledged king if his relatives of the woods could have understood the regard in which he was held by his white-skinned and clothes-wearing jailers. You will probably cut out that paragraph and put it aside for further consideration, remembering that there are at least three volumes in your Popular Science set at home, that on zoölogy, that on geology, and that on anthropology, in which there will be an abundance of interesting and authoritative matter bearing on this most important subject—for important you will consider it now that the death of a kind of caricature of humanity in the zoölogical garden that had so long amused the children as well as their elders with its humanlike motions, habits, looks, and pranks, has suddenly brought the whole question up among the news of the day, affording you a new light on a matter which you had hitherto thought to belong exclusively to the field of the professors of zoölogy and their students. Hereafter you will disposed to take a broader view of all these things, and will be in a better position to understand and enjoy the discussions of learned scientists when they are interviewed by newspaper men on subjects of this kind. The inquiring spirit of the time requires this concession even if in your private opinion there is no real relationship between men and apes. And, without regard to any such questions, you will find the volume on anthropology immensely interesting and informing.

Finally, as your morning's trip comes to an end, your attention is recalled from the natural to the mechanical sciences. You descend from your car or train, to go to your office. Your now fully awakened mind, alert to all the scientific relations of everything about you, can no longer keep from dwelling upon the underlying meanings of this marvelous display of realized human dreams. With the speed of the wind you are carried deep under the city's pavements, inclosed in a little flying parlor, in the midst of an artificial subterranean daylight, far beyond the reach of the solar rays, emulating the self-luminous creatures of the deep sea bottom; or you go shooting past the window of third, fourth, and fifth stories, or even above the levels of roofs, and you cannot but reflect and marvel that electricity does it all; electricity, that strange imp with blue star eyes no bigger than pin points, and a child's crown of little crinkling, piercing rays, which seemed so amusing when you were at school in the old days of frictional electric machines, when it was a great joke to give the cat a shock and see her flee with a squall, her hair standing on end in spite of herself. But now electricity has become a giant of unrivaled and terrific power, spurning the heavy-limbed Brobdingnag, steam, from its swift path, and fast making the world all its own—except its master, man, who is still, however, half afraid of his new and all-capable servant.

EXHIBITION OF COPIES OF PREHISTORIC PAINTINGS FROM THE CAVERNS AT ALTAMIRA, SPAIN

Painting by Chas. R. Knight. Photo, American Museum of Natural History

THE SABER-TOOTHED TIGER THAT ROAMED OVER NORTH AMERICA IN PREHISTORIC TIMES

This modern genie of limitless power, conjured out of his deceptive bottle, can do the smallest as well as the greatest things for you. When, upon reaching your office, you telephone to your wife that Mr. Blank will be home to dinner with you, you cannot form the slightest idea of how the miracle of distant speech is accomplished unless you are either an electrician yourself, or have read intelligently upon the subject of the applications of electricity to the motivation of all kinds of machinery, a subject to which an entire volume is devoted in our series. It would be a kind of shame and reproach to an intelligent man to be ignorant of the way his telephone works, and of the simple scientific principle on which it is constructed. If telephones, and such things, were products of nature and grew on trees, we might be excusable for not knowing exactly their secret; but being made by men, with the same limitations as those that circumscribe us all, we ought at least to understand them.

Thus, by a simple review of the series of common happenings that arrive every day to everybody, we perceive how intimately and indissolubly the various branches of science treated of in this compact library of science, are linked with all that we do, including our most unconscious acts and our most habitual subjects of thought. We have taken for illustration the morning history of a person supposed to live amid urban or suburban surroundings. Equally illuminating would be that of an inhabitant of a village or a rural district, and even more suggestive in many respects. The dweller in the country is brought into closer association with the infinitely changing aspects of nature than the city dweller enjoys. The simplest incident in the life of a person living on a farm may be the beginning of a thread of connection leading, like the clue of a labyrinth, into the heart of some of the most marvelous departments of science, and resulting in a mental revolution for the fortunate person who follows out the clue under such guidance as these volumes afford. The writer has remembered from boyhood the indelible impression made upon his mind by the finding of an Indian arrowhead in a recently ploughed field. The shapeliness of the beautifully chipped piece of flint, almost as translucent at the edges as horn, the delicate tapering point which, as if by miracle, had remained unbroken probably since colonial times, the two curious little "ears" carefully formed on each side of the flat triangular base to facilitate attachment to the head of the arrow, and the thought, suggested by older persons, that this weapon might actually have been used in some midnight attack on a white settlement, made more terrifying by the frightful Mohawk war whoop and the display of the reeking scalps of human victims in the glare of burning stockade and cabins—all these things bred a keen desire to learn the particulars of the history of the red warriors of the Five Nations, the "Romans of the New World," and also to know something about the life and customs of this strange, savage race of mankind which continued to live in an "age of stone" on a continent that had never known civilization. No volume like that on the history and development of man in this series existed at that time; but if such a book had existed and had fallen into the hands of the finder of the arrowhead, it would surely have fascinated him more than "Robinson Crusoe" did, because a boy can distinguish as readily as a grown person the superior interest of the true over the pretended, provided that the true possesses the real elements of romance.

So, too, the writer remembers having an interest in mineralogy awakened in his mind, never to be obliterated, by the sight of another plowed field, in the southern skirts of the Adirondack Mountains, whose freshly turned furrows glittered in the sunshine with thickly scattered quartz crystals, some of the larger and more perfect of which blazed across, the whole breadth of the field, like huge diamonds, and made the heart of the finder beat with an excitement akin to that of the discoverer of a Koh-i-noor. There were also some very curious "stone buttons" which one could break out with a hammer from slate rocks along the Schoharie Creek, and which, when cracked open, were found to be composed of pyrites that resembled pure silver—and sometimes gold—freshly broken. Now, things of this sort are always attracting the attention and awakening the curiosity of children living in the country, but the real pleasure and instruction that they might afford are usually missed because of the lack in the family library of popularly written books on the natural sciences—a lack that we are trying to supply.

For city children and their elders, whose eyes are constantly greeted, not by hills, creeks, ponds, rivers, woods, and fields, but by sky-aspiring buildings, railroads elevated on stilts, multiple-decked suspension bridges, electric power houses, tunnels that form a second city underground, and the thousand marvels and splendors of electric illumination at night, the volumes on physics, mechanics, and electricity and magnetism have a more immediate interest and value. What the children learn about these things in school is far from sufficient to satisfy their curiosity. They need books at home to guide their inquiries as well as to answer them. Only by that means can the diffusion of scientific knowledge, and the popularization of the scientific method of getting at the truth and the meaning of things be thoroughly effected. Science, as its history plainly demonstrates, progresses most rapidly only when a great number of minds have been led to concentrate their powers upon its problems. Great genius, it is true, rides over obstacles; yet consider how much further its energies might have carried it if the obstacles had been more or less completely removed in advance. Many a young man has been led to a brilliant career, to the great advantage of his country and his time, as a result of the interest awakened in him by the clear statements of a popularly written book on some branch of science.

One of the difficulties that persons unfamiliar with certain branches of science encounter in reading about them arises from the excessive use of technical terms, the lack of simple illustrative examples, and also, sometimes, a lack of sympathetic appreciation of the reader's difficulties. It has been a special object of this series to avoid this trouble. Ordinary textbooks are prepared for students in school and are intended to be supplemented by the personal instruction and guidance of a teacher, standing at the pupil's elbow, or readily approachable. But the reader who wishes to inform himself upon some progressive branch of science after his school days are over needs to have the teacher included in the book itself.

Then, too, there are many persons who have no comprehension of the great and gratifying power that a knowledge of some of the elementary principles and formulas of science bestows upon anybody who may take the little trouble necessary to master them, a trouble that does not imply a long course of scientific study. The "man in the street," if he possesses these easy-working keys to knowledge, can verify for himself some of the calculations of scientists which, if he did not know how they were done, would always remain for him in the category of the mysterious achievements of genius.

To illustrate, let us take a simple example—that of the Newtonian law of falling bodies. Many persons would assume on the face of it that there was nothing in this law that could have a particular interest for them. But let us see. You will find in the volume on physics that the law is stated thus: S = ½gt², i. e., "S equals one-half of the product of g multiplied by t squared." As you look at it you would, perhaps, as soon think of picking up a complicated tool and trying to use it for some ordinary purpose. Nevertheless, let us try. "S" in the formula means the space or distance traversed by the falling body, "g" means the velocity that the force of gravity imparts in each successive second to the body, and "t" means the time elapsed during the fall. What the formula tells us, then, is that if we observe the time during which the body is falling, and then square the number of seconds involved (multiply the number by itself), multiply this square by "g," which is represented practically everywhere on the face of the earth by the number 32, and finally divide the whole by 2, we shall have the distance that the body fell. This distance will be in feet, since the number 32, representing "g," is in feet. Now, it might be a matter of life and death, or at any rate of mental discomfort against quietude of mind, to have that rule in memory and to be able to apply it. For instance, you are on your vacation and stopping in a strange hotel, where they have put you in the top story. On looking out of the window you are dismayed at finding no fire escape, or other appliance of safety, so that your only resource in case of fire would be to make a rope out of the bedclothes and let yourself down with it. But, how far is it to the ground? How long should the rope be? Are there sheets enough on your bed to furnish it? The little formula about falling bodies will answer the question for you in five minutes. First, you let some small solid object drop from the window, and note by your watch, or by counting seconds, which everybody ought to teach himself to do, how long it takes to reach the ground. You repeat the experiment two or three times to make sure. Say the time comes out three seconds. Very well, now apply the rule: The square of 3 is 9, and 9 multiplied by 32 gives 288, and dividing by 2 you have 144 feet for the height! It is to be feared that your bedclothes rope would not be long enough; you had better send to the office for something to supplement it. But if the time of fall should be only 2 seconds, which is more likely, except in skyscraper hotels, then the calculation would give you 64 feet for the height, which you might manage with the aid of the bedclothes.

MODELS OF GUTENBERG'S PRINTING PRESSES

The models show three stages of development, the first of them at the right

BENJAMIN FRANKLIN'S PRINTING PRESS

The original is now in the National Museum at Washington

This is only a single example among many that could be given to show the usefulness and interest of many of the formulas of science which the ordinary reader looks upon as beyond the reach of any person whose occupation leads him another way. But cases of equal simplicity could be found in connection with the subjects of electricity and magnetism, chemistry, medicine, physiology, etc. Sometimes it happens that a technical word contains its own definition and explanation in a nutshell. A striking instance of this will be found in astronomy, in the word "light-year." The meaning of this word stands forth on its face—it evidently expresses the distance that light travels in the course of one year. Now, since it is known by means of direct measurement that light goes at the rate of 186,300 miles per second, manifestly a light-year must be equivalent to an enormous number of miles. In fact that number, roundly stated, is no less than 5,860,000,000,000. But to what marvelous regions of thought such a term opens the way! Yonder star is 2,000 light-years distant from the earth; then its light-waves now entering your eyes left it when Julius Cæsar was conquering Gaul, and have been speeding on their way to the earth ever since! Another star is found to be 5,000 light-years distant; then the light by which you now see it started from the star when Abraham set out from Ur of the Chaldees to settle in the Holy Land, and has not found a resting place anywhere in boundless space until just now when its tiny waves break and expire on the retina of your eye! Such treasures of knowledge and tonics to thought are scattered all through the volumes of this set, the purpose of whose publishers, editors, and writers has been to accumulate such things in small compass and in crystal clearness, for the use not only of those who, after their school days are over, still wish to keep abreast of the progress of science in all its branches—as everyone should strive to do in this most scientific of all ages—but also for those who have hitherto not had the time, or the opportunity, or perhaps even the desire, to make themselves at home in the house of science.

It may be well to add a few words on the interrelation of the different subjects treated in the various volumes of the series. This will suggest to the reader himself the best order in which to take up the reading of the books. Naturally he will desire to obtain both a clear general view of the whole field of science, and also more detailed acquaintance with its special parts, the amount of detail depending upon his particular interest in a subject. For the first purpose the preferable way would be to run first over the brief account that follows in this volume, of the history and development of science in general, and then to take up the simpler and more easily grasped branches.

But it should be firmly kept in mind that, fundamentally, science is one, having in all its branches but one aim and object, viz., the ascertainment and demonstration of the exact truth of things as far as human capacities are able to reveal and comprehend such truth, and also but one method of procedure, which is the method of common sense trained to the utmost attainable exactitude in observation and the greatest possible clearness and precision of reasoning. Science properly so-called confines itself to things that are subject to observation by the senses and to verification by repeated observation and experiment, while its reasonings and predictions are based entirely upon the unvarying sequence of the phenomena of nature, as they display themselves before us.

Science is just as one and inseparable as life, or as an organic being, and its divisions no more imply lack of unity than do the various organs and limbs of an animal, or a tree, or the different structural parts of a building. Astronomy is not entirely independent of geology, nor geology of botany, nor botany of chemistry, nor any of these of physics, nor physics of electricity and magnetism, nor the last of physiology and medicine. Accordingly the question where to begin in studying science is not one that can be answered in the same way for everybody. But the spirit is the same in all the branches.

Perhaps the best general indication of the order in which a person who has no predilection for any one branch of science should take up the various parts is afforded by their historic development. This was a result of the natural reaction of man's mind to its surroundings. The things nearest to him, and most immediately important, first attracted his attention. The broadest division would be into the science of things on the earth's surface; the science of things above the earth, in the air and the sky; and the science of things within the earth, concealed from immediate view.

If we take these in their order they naturally subdivide themselves as follows:

1—Things on the Earth—Explained by

(a) Anthropology, the Science of Man and His Ancestors, treating of his nature, origin, development, division into races and tribes, society, industry, etc.

(b) Zoölogy, the Science of Animal Life, treating of the "lower animals," and of animal life in general as distinguished from the kingdom of the plants, although the related science of biology deals with both plants and animals, its special subject being the phenomena of life in its widest sense.

(c) Botany, the Science of Plant Life.

(d) Geography, combined with Physiography, the Science of the Face, or Superficies, of the Earth, dealing with lands and seas, rivers and mountains, political divisions, etc. This is covered in our series by the volume on Physiography.

(e) In this compartment several branches of science may be grouped, since they are all the product of study of things encountered on the earth's surface. They are:

Physics, the Science of the Forces of Nature, dealing with the laws of the inanimate world around us, including the phenomena relating to solid, liquid, and gaseous bodies and substances.

Chemistry, the Science of Matter and Its Changes, dealing with the atoms and their constituents, and with the combinations of atoms into molecules to form the various chemical elements, etc.

Electricity and Magnetism, the Science of Power, fundamentally underlying all other branches, and through its investigation of the nature of the constituents of atoms—the electrons—going deeper into the constitution of things than chemistry itself. In fact this science, in some respects, blends with chemistry, although it is quite separate when it deals with the mechanical developments of electromagnetism.

Medicine, the Science of Health, Physiology, the Science of the Body, Psychology, the Science of Human Behavior, Mechanics, the Science of Machinery, etc., also naturally fall into this category of Things on the Earth.

2—Things Above the Earth—Explained by

(a) Astronomy, the Science of the Heavenly Bodies.

(b) Meteorology, the Science of the Atmosphere, rains, winds, storms, fair and foul weather, the changes of the seasons, and essentially related to the new and fast developing art of aerial navigation.

3—Things Within the Earth—Explained by

(a) Geology, the Science of the Earth's Crust, or shell; which also deals with the various stratifications of the rocks, superposed one above another, and containing in the shape of fossils, and other marks, a wonderful record of the character and development of the living forms that have inhabited the earth during the long ages of the past. Of course some of the phenomena dealt with by geology are manifest on the earth's surface, and others, like volcanoes and earthquakes, hot springs and geysers, are partly subterranean and concealed from sight and partly evident by their effects on the surface.

(b) Closely associated with Geology are Mineralogy, the Science of the Constitution and Structure of Rocks and of Mineral and Metallic substances; Vulcanology, the Science of Volcanoes, and of earth disturbances in general; and the Science of Mining, which has several branches, and forms the basis of enormous industrial developments.

It is manifest, as before said, that the reader must be his own best judge as to the precise order in which to take up the perusal of the volumes in which this immense mass of scientific knowledge is presented. But, where there is no predisposition to choose one subject rather than another, or where there is a desire to follow, as nearly as may be, the natural line of development of human knowledge, it would be well to take first, after the history, the volume on astronomy, a science that from the beginning has had a peculiar power to awaken intellectual curiosity; then that on anthropology; then the various so-called "natural history" subjects, leaving the mechanical and the more technical subjects for the last.

Or, the reader might first take up the subjects of personal importance to every human being—Medicine, the Science of Health; Physiology, the Science of the Human Body; Psychology, the Science of the Mind—every one of which is essential to the proper care and preservation of life; and afterward study the other branches in the order already suggested.

Garrett P. Serviss

CHAPTER I
HISTORY OF SCIENCE

The romantic history of science shows how the discoveries of the greatest human minds, slowly operating since the remotest times, have made possible our present-day civilization. Few studies are worthy of greater attention; no other department of knowledge affords more real pleasure. Whoever clearly understands the history of science possesses intellectual advantages over those who are ignorant of the causes that have led to the establishment of the basic principles of our modern industrial arts and applied sciences. Standards of comparison are furnished by the history of science which illuminate many of the wonders of to-day, develop alertness of mind, and afford a never-ending train of suggestions for thought.

The term science means knowledge. It was derived from the language of the Romans. It is well to have a clear idea of the meaning of the word. Everyone knows that it has to do with certain kinds of knowledge; few know the particular kinds it embraces. It does not mean the mere knowledge of a single fact. It does not mean a knowledge of something which has to be done. Long before science was born, our early ancestors observed many isolated physical, philosophical, and religious facts. They knew that day followed night, that the stars moved, that every day the sun progressed over the arch of the heavens. Such facts did not constitute science.

What we know as science began when man commenced to compare one fact with another, to classify phenomena, and to arrange his knowledge systematically. Order, method, system, are basic principles of science. The best description would, therefore, appear to be systematized knowledge of any kind which had been gained and verified by exact observation and correct thinking. The whole field of human knowledge is now methodically formulated and arranged into rational systems. Modern science may, therefore, be said to embrace all our exact knowledge. Its province is enormous; its subdivisions are limitless.

Science takes no account of knowledge which is not exact. Many people acquire valuable information which they profitably use in business, but which they are unable to communicate or describe to others because they do not actually understand it.

Farmers and flower growers often possess important practical knowledge of facts which are embraced by the principles of the sciences of agriculture, botany, and biology. But their practical knowledge is not true science. It is rather like an artist's intuitive impulse. It is not the result of scientific analysis, and there is no tangible, communicable residuum.

There could be no science if men did not discover principles of knowledge which can be communicated to, and made available for use by others. Scientific knowledge must be stripped of all traces of emotionalism and personal convictions. True science is, therefore, depersonalized knowledge.

The history of science shows how our exact knowledge has been developed along irregular paths but with progressive advances. There have been long periods during which little apparent progress was accomplished, which have been succeeded by others made memorable by brilliant discoveries.

We must constantly bear in mind that many of the truths generally accepted to-day were doubtful or novel theories at some previous period. The history of science shows the enormous mental effort expended in testing and developing what now appear to us as commonplace truths.

Basic principles like those of algebra, geometry, and the planetary motions were tested during several thousand years before they were finally accepted as true.

The human intellect at the dawn of history was similar to what it is to-day. But it was not exercised as we exercise ours because it did not have adequate materials and opportunities. For the same reason science made slower progress in early times than it does now. Progress is cumulative. Each advance helps that which follows. The functions of a scientist are to struggle against individual views, and to provide an explanation of phenomena which may be accepted as true by other minds. Ascertained facts must be classified and then sequence and significance recognized from an unbiased viewpoint.

The history of science is the written record of countless experiments, theories, and experiences of mankind which have been submitted to the tests of scientific methods.

While it is true that science embraces all knowledge its real scope is limited to knowledge which is reducible to laws and can be embodied in systems. The human mind unites all knowledge by a single thread, but we have to chart and map it into larger and smaller divisions which we define by the methods, basic concepts, and plans used in developing them.

We may now see how it is that the boundaries of any science are merely approximate. The general grouping of the sciences is likewise approximate. The first large group includes the abstract, or formal, sciences such as mathematics and logic. The other great group comprises the concrete sciences dealing with phenomena as contrasted with formal relationships. Chemistry, biology, physics, psychology, and sociology belong to the concrete group.

At the beginning of history man is discovered observing the great phenomena of Nature and struggling to learn their laws and to explain them. Religion is both emotional and intellectual, and through these qualities it attracted primitive man while he was attempting to gather light on the riddles of the world. It was through religion that science was born.

Recent researches into primitive beliefs have shown in a surprising manner the psychological unity of man. In all parts of the world, in all periods of history, and under all conditions, the minds of men, in their natural reactions against the basic factors of existence, operate in similar ways. There is a remarkable resemblance in the mental processes of men. The laws of thought appear to work automatically in all men. The minds of prehistoric people worked like those of men to-day. The impressions of the senses appear to be interpreted in similar ways by all peoples. Here is the explanation of the numerous resemblances we find in national histories, national folk lore, and national religions. They differ much in innumerable details, but possess many resemblances in their great fundamental conceptions. Normal man has always been religious. Mankind has always assumed definite attitudes toward the universe and this has resulted in the universality of religion.

Early men the world over appear to have been as eager to learn the keys to the riddles of the universe as was the boy Longfellow sang about in the following stanzas:

Nature, the old nurse, took
The child upon her knee,
Saying: "Here is a story-book
Thy Father has written for thee."

"Come wander with me," she said,
"Into regions yet untrod;
And read what is still unread
In the manuscripts of God."

And he wandered away and away
With Nature, the dear old nurse,
Who sang to him night and day
The rhymes of the universe.

And whenever the way seemed long,
Or his heart began to fail,
She would sing a more wonderful song,
Or tell a more marvelous tale.

Modern science has developed from this instinctive human desire to read Nature's story-book and understand her marvelous tales.

Early struggles of mankind taught that human behavior must be regulated in accordance with rigid moral laws. This promoted the primitive social processes which were early concerned with religious beliefs as well as with magic and medicine. Two of the earliest beliefs universally accepted were that we possess souls and that our personality persists after death. These basic principles of faith have caused extremely beneficial results to follow in the development of knowledge.

Some of the American Indians and other primitive peoples of to-day still live in the belief that the heavenly bodies, the sky, sea, and earth, as well as plants, animals, and men, all belong to a vast system of all-conscious and interrelated life, in which the degrees of relationship are distinguished by the degrees of resemblance.

Religious beliefs were developed from struggles to conceive the inconceivable and discover the infinite. Religions led to studies of mysteries and ceremonies and rites. Magic developed and this also had its customs, dogmas, and rites. The difference between magic and religion was that the magician was consulted by his personal friends, whereas the holders of religious beliefs had a common bond uniting them in one strict form of worship. Magic was not systematized, while religion was a unified system of beliefs and practices relative to sacred things, and chiefly to the regulation of moral concepts and conduct.

The intimate association of religion, magic, necromancy, and science continued until the early Greek era. There were many temples erected in Greece and dedicated to Æsculapius, the god of medicine. Cures were believed to be effected through the valuable offerings made to the god by patients and their friends. It was thought that the ways to health would be indicated to them by the god through dreams.

Recent investigations of the representative ceremonial rites of the aboriginal peoples of Australasia and of North and South America have yielded a remarkably rich fund of information on the causes and conditions which operated in prehistoric eras in developing the mental, moral, and physical sciences.

Some of the most romantic stories ever developed by the human intellect are to be found in recent scientific works dealing with the history and principles of the tribal customs, ceremonies, and religious rites of primitive peoples. The early chapters in the history of man's mental development and the evolution of science from distant origins in mystic forces, through magic and necromancy to religion and philosophy, must give abundant pleasure to all thoughtful persons by showing how it came that the high state of civilization now attained was brought about by slow processes, operating through immense periods of time and blossoming only during the past two or three thousand years. A study of these stories cannot fail to show how intimately science has been associated with religion, why every normal individual is essentially religious, and why the continuation of our civilization, and the very existence of the human race, are absolutely contingent upon the recognition of the moral laws, in the future as in the past. The history of science establishes the fact that moral sanctions, which require religious ceremonies to keep them vital, are the essential bases of human progress.

CHAPTER II
PRIMITIVE MAN AND EARLY CIVILIZATIONS

The development of scientific history has not followed a uniform course. Progress has been rhythmic. There has been always a reaction coming in the steps of brilliant discoveries. Periods of feverish experimental activities have been succeeded by others during which little apparent progress was made.

Such dull intervals seem to have been necessary for developing, formulating, classifying, and testing the innumerable details and inferences that the discoveries of the active periods produced.

While mankind in general has contributed to the total of our intellectual treasures, some races have been more active in this way than others. For this reason it is advisable to briefly survey the more recent discoveries about the ancestors of existing peoples.

Indo-Malaysia, parts of central Asia, and the valleys of the Tigris and Euphrates rivers in Mesopotamia are variously credited with having been the cradle of the human race. It should be understood, however, that we are only permitted to speak authoritatively of existing races, because the land forms of the earth have undergone such remarkable changes that we can know little definitely about the earlier periods of human history. For the purposes of the history of science, while bearing in mind these qualifying suggestions, we may accept the statement that man's ancestors originated in proximity to India.

It was around the waters of the Persian Gulf that the earliest known civilizations arose. The people who founded them came from central Asia. They had reached a considerable degree of culture, which suggests that they themselves came from earlier centers of civilization.

The study of prehistoric antiquity is termed archæology. Its principal periods have been divided, for convenience, into the Stone, Bronze, and Iron Ages. Each of these is distinguished by the substances used for tools. In the Stone Age men used stone spearheads, arrows, and knives, whereas in the Iron Age similar things were made of iron or copper.

The science of mankind is known as Anthropology. It deals with the innumerable steps in the evolution of mankind from remote periods, and with the primitive development of the arts, sciences, and religion. Yet it is one of the youngest of the sciences.

One of its essential teachings is that heredity and racial predispositions play, and always have played, more important parts in man's evolution, and in the development of civilization, than environment and education.

Hereditary tendencies, such as the religious, moral, and æsthetic instincts have been indispensable in preserving and developing all the races of mankind.

Moral discipline has been the chief factor in self-control, and therefore in civilization. It is because the moral sense has proved so beneficial to the human race, and is the most powerful of our instinctive desires, that mankind always has been and must be religious. It controls man's knowledge, desires, and will, and has dominated the race since our early ancestors began to think.

When we recognize this fact we can readily see that anything which tends to oppose the moral or ethical sanctions, or detract from religious beliefs, is injurious to civilization and human progress. The histories of religion, ethics, and æsthetics plainly develop the rôles which have been played by moral self-discipline in the protection and development of mankind, as well as of knowledge and science.

The moral control of individuals acts also upon society generally, and upon whole racial and national groups. The ethical ideals assist each individual mind to realize its own end and at the same time tend to influence the tribal and social mind to attain a common end. This great moral, instinctive force, which has played such an immensely valuable part in developing civilization and science, is known as the human social and national conscience. It acts both individually and collectively.

European races have been divided into classes corresponding to the prevailing cephalic indices. The longheads are grouped as the Nordic, or Baltic, subspecies, because they were formerly numerous around the Baltic countries. People of this group are distinguished by tall statures, fair skin and hair, good physique, and light colored eyes. These peoples include the Scandinavians, Anglo-Saxon, and certain important Teutonic groups, as well as Asiatic peoples who are known as the Aryans.

Copyright, Ewing Galloway

MODEL OF THE SAILING VESSEL "SANTA MARIA," THE FLAGSHIP OF COLUMBUS

CURTISS NAVY RACER, THE AIRPLANE THAT WON THE PULITZER RACE OF 1921

U. S. ARMY DIRIGIBLE ON A TRANSCONTINENTAL FLIGHT

The most important rôles in the development of modern civilization, art, industry, and science have been played by representatives of the Nordics.

The Iberian, or Mediterranean, subspecies, ranks next in importance. The peoples of this great racial division originally occupied the countries between the northern Atlantic coast of Africa and the confines of the areas of the Nordics around the northern provinces of France. They spread down the Mediterranean and over large areas in Asia. Their skulls are long, but differ from those of the Nordics in their absolute size. Their stature is lower, and weaker than that of the Nordics, while their hair, eyes, and skin are dark or black. The Welsh, the Moors, and the early Greeks are chiefly classed with the Mediterranean group. The Carthaginians, Phœnicians, Egyptians, and Etrurians were members of it.

The roundheads comprise the Alpine subspecies. This is the strongest numerical group to-day. It is characterized by small round heads, short bodies, dark hair, and dark eyes. It is of Asiatic origin and includes the Slavs, modern Greeks, Italians, Germans, Austrians, Swiss, the pre-Nordic Irish, French, and Belgians. The first Alpine invasion of Europe began about 10,000 B. C. There were many subsequent ones through the plateaus of Asia Minor, the Balkans, and valley of the Danube. They reached England about 1800 B. C., and formed small colonies in Ireland, the descendants of which now call themselves Celts and are clearly distinguished by the characteristic Alpine indices. This race is now so well acclimatized in Europe that most of its Asiatic traces have been lost, and its round skulls and dark eyes and hair are the only reminders of its Mongolian origin.

Members of each of these three great racial groups of mankind have throughout the ages contributed to the development of the sciences and arts. The Nordics began to appear in European history as agricultural tribes, speaking Aryan languages, like Celtic and Welsh, who swept down from the north and pushed the earlier settlers back through their irresistible arms, which were made of bronze and later of iron. The earlier settlers were still furnished with arms and implements of the Stone Age.

There was a much older intellectual people than the Nordics settled in Europe. The people of this race, about whom we have learned through recent archæological researches, are known as the Cro-Magnons. They lived between 25,000 and 10,000 B. C. Their skulls were distinguished from those of the Nordics by their pronounced cheek-bones and broad faces. Their culture, as their favorable cephalic index would suggest, was of a high character. Numerous drawings and art works of theirs, which have been preserved, place them among the world's superior peoples.

Soon after the settlement of the Cro-Magnons in Europe, and their intermarriage with the earlier settlers, their physical development and stature began to decline. They were finally absorbed and destroyed by the inferior peoples among whom they dwelled. Their disappearance, like that of the ancient Greeks, who appear to have been the most intellectual people the world ever produced, shows how the upward development of human physical and intellectual qualities is constantly injured by the contacts of superior and inferior races.

The scientific discoveries made prior to the Iron Age, or about 2000 B. C., were not numerous. The struggle for life was so intense that few had opportunity for contemplation and philosophic reflection. It was subsequent to the discovery of the basic principles of metallurgy, in the Iron Age, that science began rapidly to advance. The benefits bestowed upon mankind by the employment of metals reduced the sharpness of life's struggles, permitted and instigated reflection, and provided means for experimentation.

Modern history begins with the peoples of Mesopotamia. There were cultured peoples east of the Tigris and Euphrates, in Persia, India, Mongolia, Tartary, and China before the founding of Babylon. But we are more instructed about the Babylonians and Assyrians than about earlier Asiatic races.

The Babylonians and Assyrians appear to have originated in central Asia and to have migrated to Arabia about 10,000 B. C., and perhaps earlier. They were well settled in Arabia before the Egyptian pyramids and other Semitic memorials were planned. They brought with them from the farthest Orient many important contributions to civilization and culture, and developed many others.

These were religious, philosophical and keen commercial peoples. They shaped the organization of modern religions. The Babylonians reduced the world of gods to a single system with classifications distinguishing between major and minor deities, and between those of heavenly, or stellar, and earthly habitats, and those of time and space. They developed many religious myths of the Creation, the Flood, Paradise, and others which were subsequently embraced by other religions.

Both the Babylonians and Assyrians composed beautiful hymns, prayers, parables, and religious tales, and had numerous elaborate religious customs, rituals, ceremonies, and festivals conducted by priests, nuns, and acolytes.

Anu, or Anum, the God of Heaven, was the principal Babylonian deity, while Ashur was the leading god of the Assyrians.

Religious studies and rites occupied a large portion of the time of these peoples and, consequently, their temples, monasteries, schools, and other religious buildings were large and numerous. Their architecture was elaborately artistic. This was one of their incentives to scientific invention. They made important discoveries in all the basic physical sciences, like chemistry, physics, metallurgy, and mathematics, to enable them to improve their buildings and to embellish them with paintings, pictorial tiles, and fancy metals and textiles. They had excellent professional men, artists, jurists, bankers, contractors, and scientists. They were fond of literature and founded extensive libraries. Music and musical instruments were very popular with them. Their cuneiform writings, as disclosed by numerous beautiful stone and porcelain tablets which have come down to us, were excellently done.

The fragments of literature, laws, and religious policies that we are acquainted with indicate that the numerous Babylonian and Assyrian settlements in each great empire possessed social and political conditions similar to those of our days. Science and art were then sufficiently advanced to enable these ancient people to live as agreeable, moral, and legally secure lives as those of any subsequent peoples.

The Chinese appear to have been making similar progress to that of the Babylonians about the same period. It would seem that both these peoples were in contact with a similar but earlier cultured race in central Asia. Although the early Chinese were a religious people, they appear to have been more philosophical than the Babylonians. This enabled them to make further progress in the abstract sciences. In subsequent years they made rapid strides in the physical sciences, as will be shown later.

The Egyptians came into prominence toward the end of the Babylonian and Assyrian empires, and for many centuries played a great rôle in developing civilization. The numerous benefits which they bestowed upon the world by their researches in science and art are not fully appreciated.

Early history pictures two great Asiatic races struggling for supremacy in India. They were the Aryans, a fair-skinned people, and the Dravidians, a colored people. The Aryans succeeded in displacing the Dravidians in the great plains, upon which they settled and developed large cities, important world commerce, and contributed great art works and scientific and philosophical discoveries to the world's stores. The Dravidians retired to the hill country, where their representatives still live.

The minds of the various Indian peoples have always been strongly philosophical. This led them to the development of numerous religious sects and philosophical systems, and they made important mathematical discoveries. While the scientific bent of the ancient Greeks was of a concrete nature, which tended toward geometrical proofs for scientific problems, that of the ancient peoples of India was toward numerical symbolism and arithmetical proofs. We find that when the Greeks were developing geometry the Indians were contributing to arithmetic and algebra.

The Chinese closely resembled the ancient Indians in the philosophical tendency of their minds; but, owing perhaps to the different conditions under which they lived, they were more concrete in their ideas. They also made progress in mathematics and developed medicine, chemistry, metallurgy, and many of the sciences which were applied to commercial and industrial uses. The progress made in mathematics in China was transmitted to Egypt, and therefore to Europe, through India. Among early Chinese discoveries in mathematics were methods of solving numerical equations and the development of magic squares and circles, which gave a great stimulus to studies in geometry and astronomy.

The Arabs, Greeks, and Romans took up the discoveries of the Asiatic peoples, and the Egyptians enlarged them and passed them forward to us. The Arabs solved cubic equations by geometrical means, perfected the basic principles of trigonometry, and made great advances in mathematics, physics, chemistry, and astronomy.

A survey of the early history of science indicates that from the remotest period man was engaged in grappling with the great principle of causation. Progress was necessarily slow at first on account of the scarcity of tested data. Then it became more rapid. Soon after the founding of the great city of Babylon we find that the Babylonians were possessed of enough knowledge of the arts and sciences to enable them to become world traders and great industrial undertakers. They built many cities and lived highly civilized lives. The history of modern science may very properly be dated from the building of Babylon.

CHAPTER III
PRE-BABYLONIAN SCIENCE

The transcending wonders of the phenomena of the heavenly bodies attracted the attention of primitive man at an early period of his intellectual development. The succession of day and night, the phases of the moon, comets, meteorites, the eclipses of sun and moon, the recurrence of the seasons were observed and recorded. In this way, through long uncivilized times, many scientific facts were noticed and handed down by tradition, and probably were among the first scientific data collected. We have no means of determining when the primitive science of astronomy became systematized, although there are reasons for believing that it was roughly outlined at a remote date.

There was a tradition among the Babylonian priests that their astronomical observations and records went back to a period of more than 400,000 years. This statement was believed by the people of antiquity, and was made to Alexander the Great during his Indian campaign.

Astronomy appears to have been developed into an organized system by the primitive peoples of central Asia. It was carried to China, India, and Arabia by learned travelers. There were government astronomers in China before the year 3000 B. C., and history records that two of these officials, named Ho and Hi, were beheaded in the year 2159 B. C. for being careless in their work and failing to issue a timely prediction of a solar eclipse.

Chinese history also relates that the Emperor, in 2857 B. C., issued an edict recommending the study of astronomy. From these and other historical references we learn that nearly 5,000 years ago astronomical science was not only well developed, but that its educational value was recognized.

While attention was being given to the study of astronomy in China, this science was independently developed in India. The astronomers of India invented a different system from that of the Chinese, and compiled numerous astronomical tables which were published and widely used as far back as 3102 B. C.

These early astronomical studies resulted in the division of time practically as we know it to-day. The Babylonians had a week of seven days. The days bore names of the planets and were divided into hours and minutes. Days were combined into months and years. The Babylonian and Chaldean astronomers, like those of China and India, were important men and were credited with great learning.

The Babylonian month began on the evening when a new moon was first observed. An adjustment was made necessary between the months, owing to the fact that the actual lunar interval is about twenty-nine and a fraction days. Numerous astrological observations were made with the view of obtaining data to facilitate the monthly adjustments. The taking of these observations was made easier by maps of the heavens which were recorded on baked clay tablets and prisms. Similar maps of the world, with positions fixed by astronomical observations, were likewise made in Babylonian times.

The usefulness of astronomical observations and predictions led to the belief that they could be employed with advantage for wider purposes. The astrologers endeavored to deduce omens and forecast horoscopes. In order to facilitate their calculations, the astrologers invented calculating and time-dividing machines. Tablets from the royal library at Nineveh indicate that Chaldean astrologers possessed mechanisms which divided the hours of the day by mechanical means. These were forerunners of modern clocks and timepieces.

These early scientists represented the earth as a vast circular plain, intersected by high mountain ranges and surrounded by a large river, with other mountain chains which lost themselves in an infinite ocean. The heavenly vault was believed to be supported by the highest peaks of the outlying mountains. It was owing to the peculiar nature of this cosmogony that the pre-Babylonians and Babylonians were unable to develop a satisfactory mechanical view of the world. The world had to wait for an adequate mechanical theory before general knowledge could be advanced, so that men like Newton and Laplace could correct the errors of early theories and furnish a sound working hypothesis.

The advancement of science requires methodical observations and the use of the highest powers of the imagination. It is thinking in picture-like figures that supplies primitive reasoning. While pure reasoning deals with abstract, verbal images, the more concrete picture-thinking deals with object-images. The differences between thinkers and dreamers is chiefly in the way their minds act. But even thinkers are supplied with thought material by the elementary mental operation of picture-thought, dreams, or dream-thinking. Science needs the active use of the imagination to anticipate experience and suggest the issues of a process in course of action. Most great inventions, and probably all primitive inventions, were stimulated by imagination. But the imagination, unless skillfully directed, is liable to numerous errors. That is why in all ages there has been much error in connection with knowledge. There could, however, be little or no progress without imaginative work. It is only within very recent years that the modern sciences have been stripped of much absurd matter derived from crude imaginative work. When we bear this in mind, we have the key to the part played by ancient myths, magic, and ceremonies in developing civilization.

The term magic is derived from the Persian term for priest. The magi, or priests of Zoroaster, their religion, learning, and occult practices had important world-wide effects just before the Babylonian era. Magic is a pioneer of religion, philosophy, and science.

Medicine was benefited, in some ways, by the priests seeking means for dealing with the work of the spirits of evil. Chemistry and metallurgy were also advanced, and new realms of knowledge were opened even by magicians.

The magic of the Babylonians survived their empire. It was handed over to the Egyptians and contemporary peoples, and was in turn passed down to the magicians and alchemists of the Middle Ages, and to the dramatists, poets, and novelists of all ages.

The accumulation of scientific facts was greatly facilitated by the improvements made by the Babylonians in the manufacture of earthenware tablets, scrolls, and prisms. Beautifully drawn cuneiform picture signs recorded on these all the knowledge of the day. These stonelike records were filed away in many monasteries and libraries. Subsequently, letters were invented, alphabets were formed, and writing displaced the hieroglyphic symbols.

The invention of alphabets made reading easier. This resulted in giving an impetus to education which has had cumulative effects right down through the ages.

We are now in a position to realize why scientific discoveries were made very slowly, and at long intervals apart, in early times. Facts had to be accumulated, studied, grouped, and compared. Accounts of these studies had to be pictured and stored away for future use. Only exceptionally learned men did this. But when alphabets were invented and education increased, numerous minds became active and there was a great extension of thought, experimentation, and philosophical contemplation. This was followed by the establishment of new religious houses, schools, and philosophical academies, at all of which the ablest men of the day emulated the scholars in formulating theories and making inventions.

Soon after the perfecting of cuneiform writing in Babylon, characters were devised for representing numbers. A vertical, arrowlike wedge represented the figure 1, while a horizontal wedge stood for 10. A vertical and horizontal wedge, placed together, signified 100. Other arrangements of these characters meant that they were to be multiplied, subtracted, divided, or added together. In this simple manner all kinds of arithmetical results could be recorded.

The Babylonian mathematicians were familiar with decimals, integers, and fractions, and their tables and records of astronomical and engineering calculations reveal a remarkably high degree of mathematical ability, indicating that peoples who preceded us by several thousands of years were familiar with the more important calculations requisite in trade and industry as well as for astrological computations.

Babylon was a great world metropolis. It occupied a position similar to that occupied by London to-day. Its merchants were engaged in world-wide commercial operations which needed good systems of bookkeeping and accountancy. These, in turn, presupposed a highly developed arithmetical system. Practically all the arithmetical calculations used in commerce to-day were employed by them. Their accountants, like those of China to-day, used the abacus, or calculating machine.

A lucid illustration of the accuracy of ancient calculations, the efficiency of their reports, and the confidence with which they executed intellectual duties is afforded by the following translation of a Babylonian astronomer's official report:

"To the King, my lord, thy faithful servant, Mar-Istar.

"... On the first day, as the new moon's day of the month of Thammuz declined, the moon again became visible over the planet Mercury, as I previously had predicted that it would to my master the King. My calculations were accurate."

The records of Babylon furnish us with a wealth of documents of this character.

The numerous peoples of India have always been divided into castes. This has resulted in the pioneering work in science falling to the priests. However, the principal priests were among the most intellectual men of each generation and, as they traveled in search of instruction, India was always in contact with the progress made in China, central Asia, and Babylonia. These great centers of ancient learning progressed together.

The Indians were able mathematicians and discovered and developed at an early period what is now known as "Arabic notation." In this work they were assisted by the Babylonians.

The Indians, like the Chinese and Babylonians, solved problems in interest, discounts, partnership, the summation of arithmetical and geometrical series, and determined number changes in combinations and permutations with ease. They were also proficient in algebra, the extraction of the roots of numbers, various classes of equations, and the principles of trigonometry.

The Chinese have always been good mathematicians. It is probably due to this fact that they have at all times been such able traders and bankers.

We are not so familiar with the works of Chinese mathematicians in pre-Babylonian times as we are with the Indian; but the references of contemporary writers indicate that the Chinese scientists were as able and active as their contemporaries.

We have remarked the high degree of perfection which was attained in the Babylonian era by scholars in science and mathematics. Similar perfection was attained in art, industry, law, and medicine. The wonderful law work that has come down to us under the name of the code of Hammurabi indicates not only the extensive progress which had been made in law, but incidentally through its references the progress of agriculture, industry, commerce, and business.

Many references in the Hammurabic code, written about 2300 B. C., show that the medical profession had attained considerable advance in Babylon. Surgeons were daring operators. They commonly performed operations for cataract. Many of the common major operations now performed by surgeons were also done by the ancients. They were experts at setting fractured bones. The physicians made effective use of drugs. Many drugs employed to-day were known to them.

The discoveries of the early oriental nations were collected and developed in Babylon. The entire fields of science, mathematics, geometry, agriculture, astronomy, philosophy, and art were focused in Babylon and handed down to the Egyptians and the Greeks. Much credit that is given to ancient Greece should be shared also by Babylon. It was from Babylon that Greece obtained the principles of its civilization, arts and sciences. Even Greek architecture and sculpture were originally derived from Babylon.

CHAPTER IV
EGYPTIAN SCIENCE

The early civilization in Egypt developed in the ancient cities of Thebes and Memphis. Authorities on the dawn of history in Egypt are unable to definitely account for the origins of the various peoples who have ruled the land. One school contends that the early negroid inhabitants originated in Africa. Another school opposes this view and suggests an Asiatic origin. Each of these schools can marshal facts to sustain its contentions. The truth is that Africa was inhabited at such an early period that we are unable to fully trace back the movements of its races.

Man was divided into species and subspecies at a very remote period. The dominant peoples in each country, in each era, were the successful contestants in long conflicts for supremacy. Many races have vanished without leaving any traces beyond reversional strains which still come to the surface at times in families living to-day. The laws of evolution, only recently deciphered, are the sole means we possess for learning about many of the long-perished species of men.

A few races, too weak to ever gain supremacy and themselves to occupy districts, or countries, have survived by dwelling among stronger races. The Ainus, in Japan, and the Jews in Asia and Europe, are well-known examples.

MODEL OF AN EARLY ELECTRIC MOTOR

The original was invented by M. H. Jacobi in 1834 and was used in 1838 to propel a boat on the Neva at St. Petersburg.

MODEL OF AN EARLY TURNING LATHE

This mechanism was invented by Thomas Blanchard in 1843. He also invented a lathe for turning gun barrels.

Copyright, Underwood & Underwood

AN EDISON PHONOGRAPH OF 1878

The sound record was made on a sheet of tin foil vibrated by the voice.

WHITNEY'S COTTON GIN

This device, invented in 1793, revolutionized the cotton and cotton manufacturing industries.

Egypt, owing to its remarkable geographical situation between Asia, Europe, and the vast continent of Africa, has been a great highway for race migrations. Many peoples have lived and ruled there and passed on before incoming tides of new and more vigorous peoples. Each race, undoubtedly, during its residence in Egypt contributed to the general fund of Egyptian knowledge and customs and assisted in the development of science.

The tombs of Thebes have given us bodies of ancient Egyptians of more than six thousand years ago. At that time the people were characterized by the Grecian type of profile. They resembled the contemporary active peoples in India and Arabia and did not differ much from the Egyptians of our day. The incoming streams of people who settled in the Nile valley, both Asiatic and negroid, changed the appearance of the Egyptians at different times by intermarriage, but when their vigor waned and they were crowded out by other peoples, the Egyptians assumed their regular Semitic characteristics.

Egyptian history really begins with the old kingdom dynasties, about ten thousand years ago. The tombs of Abydos have furnished material for accounts of this early period. There were eight powerful kings in the first dynasty and all of them contributed to the advancement of civilization. Abydos, and later Memphis, were their principal cities. They ruled in great luxury and were patrons of the arts and sciences. The art works, sculptures, and carvings in ivory and ebony of this era speak in eloquent terms of the taste and high mental powers of the people. Modern museums are well supplied with relics of those times, which illustrate the degree of civilization attained by the Egyptians at the beginning of their history better than any written account.

The early Egyptians adopted the sciences, arts and customs of the Babylonians. With these as a basis the priests and learned men experimented and made many independent researches and discoveries.

The pyramids, erected near Cairo 3000 B. C., indicate the high degree of culture which the early Egyptians had attained. These renowned monuments to the kings were scientifically designed and constructed to exist for all time. In order to contribute to their usefulness, they were planned so as to exhibit correct geometrical forms and indicate the cardinal points of the compass and the positions of certain astronomical bodies. The details of their construction disclosed much mathematical, geometrical and physical knowledge, and their actual building called for not only an all-around mechanical skill but a high degree of engineering ability. They were constructed of various materials. Some large granite blocks were used in the outside walls and these were brought from the upper Nile. They were towed down the river on barges and were lifted into the positions in which they are found to-day. Various mortars and mortar mixtures were employed in binding the brickwork and masonry. These called for a good knowledge of chemistry and physics. The arches and sloping walls of some of the larger pyramids show how well the architects and engineers of the day knew their professions. With similar means in their possession, the best professional men of the present day would find it difficult to get such splendid results.

In the past few years, lapidaries and gem-workers have learned to cut stones and gems with steel disk-wheels, the cutting edges of which are furnished with carborundum or emery powder or insets of diamonds. The pyramid builders knew this method of sawing and cutting stones. They actually employed bronze saws set with diamonds to cut the huge blocks of granite, syenite, diorite, and basalt used in the construction of the pyramids. They also set the cutting ends of their rock drills with diamonds, and bored rocks as we do to-day with diamond core drills. The art of making these tools was afterward lost. Only within the past half-century have mechanical rock saws and diamond drills been reinvented. This brilliantly indicates the inventive ability of the engineers at the dawn of Egypt's history. The builders of the splendid monument of Rameses II in the Memnonium, at Thebes, which weighs 887 long tons, transported the huge stone by land from the quarries at E'Sooan, a distance of 138 miles. Such tasks appear never to have deterred early Egyptian engineers and architects. They were so sure of their ability to carry their great operations to satisfactory completion that they never hesitated in agreeing to the severest penalties for nonfulfillment of contract. Their cranes, levers, wedges, rock drills, pumps, air blowers and compressors, and building tools all showed how well mastered was their knowledge.

Their quarrying methods were similar to those used in the best practice to-day. When huge blocks and slabs of stone were needed the required dimensions were marked on the rock and channeled out. Metal wedges were forced into the channels and struck at once by a large number of hammers. The constant vibration, in time, broke off the stone with clean-cut surfaces. When these were to be carved into statuary or ornamental shapes it was often done at the quarries, so as to reduce transportation difficulties. Water transportation was used when possible. When the stone had to be moved over the desert sands it was lifted by cranes and set on sleds drawn by men or animals, or driven forward by levers, just as heavy steel machinery is moved by modern engineers.

The principle of the siphon was known to the Egyptians at an early period. It was employed daily in many homes for supplying water and for drawing off wine from barrels and tanks into domestic utensils. Its principal use, however, was in civil engineering works. Siphons were constructed on a large scale for furnishing water to villages, draining land for farming, and for irrigation purposes. They were built, in many known instances, for carrying large quantities of water, in high lifts, over hills.

Herodotus tells us that the science of geometry was discovered by the Egyptians as a result of the necessity for making annual surveys of the farming lands in the Nile valley.

When geometry was established as a practical science, land and astronomical surveying were simplified and many branches of mathematics were enlarged. The science of marine surveying was also developed and this led to a great improvement in map-making and in geography, in which the Egyptians became famous.

The skill attained by the Egyptians in land surveying required accurate surveying instruments. These were invented at an early period. The Greeks claim the invention of the theodolite and similar instruments, but Egyptian history shows that gnomons, surveying compasses, and levels were used by Egyptian surveyors long before the Greeks began to study the learning of Egypt.

Astronomical science made great progress in Egypt. The theory attributing to the sun the central place in our planetary system, now called the Copernican theory, was known and used in Egypt. They were familiar with the obliquity of the ecliptic, and knew that the Milky Way was an aggregation of numerous stars of various sizes. They understood that moonlight is simply the reflected light of the sun. The movements of comets, the positions of the principal stars and stellar constellations and other astronomical phenomena were studied and charted on astronomical maps or recorded and forecasted in astronomical tables.

The discoveries made by the Greek scientists naturally stimulated philosophical thought, which in turn reacted upon scientific experimentation and led to a broadening of the scope of general research work. We are dependent upon the pictorial records of early Egyptian times for descriptions of the instruments and machinery employed and these are not always clear. They indicate, however, that the Egyptians quickly learned the sciences developed by the Babylonians and other Oriental peoples and improved them. Their knowledge of astronomy, mathematics, geometry, chemistry, physics, medicine, and agriculture was extensive. The priests and learned men taught the pure sciences and constantly experimented; the engineers, architects, surveyors, and mechanics applied the sciences to the arts.

In one of the records of an early dynasty the father of a student sailing up the Nile to begin his studies in one of the leading scientific schools gave this advice: "Put thy heart into learning and love knowledge like a mother, for there is nothing that is so precious as learning."

The Mesopotamian peoples, as we saw in the last chapter, considered the stars and principal heavenly bodies as deities. The Egyptians did not do this, although they looked upon the heavens as the abode of all pious souls. Their astronomical knowledge at the time of the establishment of the New Empire at Thebes, about the year 1320 B. C., was remarkably extensive.

The Egyptians divided time in accordance with the course of the sun into periods of 365¼ days, and these were divided in accordance with the course of the moon into periods of about 29½ days. Thus the basis of the system of years and months used by us was perfectly understood by the Egyptians.

The science of medicine was developed at a very early period in Egyptian history. The various divisions of physicians, surgeons, pharmaceutists, veterinarians, and dentists organized by the Babylonians were retained by the Egyptians. Many names of distinguished practitioners have been handed down. Nevertheless, their anatomical knowledge remained poor, and there were many superstitious practices connected with medicine. The various medical manuals which have been preserved show that the Egyptian physicians studied diagnosis with modern thoroughness. They were aware that an exact knowledge of each disease, obtainable only by a complete study of the symptoms, was necessary before a correct treatment could be prescribed. When the magic and the superstitious dressings are abstracted from Egyptian medical works and prescriptions, we find that the broad principles were sound and efficient. They were developed along lines similar to those of modern times.

Mathematics attracted much attention in Egypt. The learning of Oriental countries on this subject was readily absorbed by the Egyptians. The Greek historians were so surprised at the efficiency of the Egyptians in this branch of knowledge that they almost unanimously asserted that the mathematical sciences originated in Egypt.

The pyramid base lines run in the direction of the four points of the compass, and were determined by correct astronomical methods. The astronomers and surveyors were skilled in trigonometry. Fractions were known to the Egyptians, who were taught in the schools of Babylon. The modern x, representing an unknown factor, was known to the Egyptians under the name of "hau."

Quadratic equations were employed by them. The problem of finding x and y, when x² + y² = 100 and x:y = 1:¾, one of the earliest problems of this character known, was found in a papyrus at Kahun. The problem was stated as follows: "A given surface of, say, 100 units of area, shall be represented as the sum of two squares, whose sides are to each other as 1:¾."

The papyrus gave the working out of the solution. Many similar problems are given in mathematical works and papyri. They show the proficiency in mathematics that Egyptian scientists had attained at a remote period. But their methods of expressing mathematical problems were crude and, consequently, involved much tedious labor in finding solutions. There can be little doubt that if effective mathematical symbols had been devised the abstract sciences would have made even greater progress than they did in early Egypt. When we study the complicated solutions of algebraic problems made by the Egyptians, owing to the lack of simple symbols, we can appreciate how greatly modern mathematical science is benefited by the devices now employed for expressing quantities, variations, and operations.

The Egyptians were expert in applying the discoveries of science to the arts. The Nile made their country potentially rich in agriculture, and they devoted much attention to inventing such things as single and double plows, rakes, and other agricultural machines, many of which were drawn by oxen, donkeys, and other animals. Reaping was done with sickles and scythes. Not only was irrigation understood and widely practiced, but the importance of fertilization was recognized.

The farmers understood the preservation of meat, vegetables, and foodstuffs generally, by drying or pickling. They also brewed beer and made wines, vegetable and seed oils, and alcohol. The selection of breeding animals and the principles of variation were understood and employed for developing particular breeds of cattle and farm stocks.

The papyrus reed grew luxuriantly in Egypt and this resulted in the discovery of paper making, weaving, thread making and many textile methods. These industries led to the invention of looms, rope and twine twisting appliances, flax weaving and other machinery. The linens and cloths made by these machines have never been excelled.

Dyeing was developed with the textile industries. As the skies of Egypt are bright, the people in all ages have had a fondness for brilliant colors. The call for bright textile colors led to a considerable development in the chemistry of dyes and dyeing. Vegetable and mineral dyes were used. Dyes were not always applied to the whole pieces of goods, but stenciling and other methods of patterning were used. The highly organized artistic skill of the people demanded art-designed textiles and the manufacturers responded with beautiful and rich materials.

The fur and feather industries became important at an early period. The Egyptians were fond of beautiful ornamental skins like those of the panther or gazelle. Such skins were manufactured into numerous domestic articles, made into clothing or used as rugs, mats, and seat coverings.

Skins not valuable for art purposes were sent to the tanners to be converted into various kinds of leather. Tanning was highly developed, and the tanners turned out leathers which are to-day admired for their excellence. The tanners carried on their industries by chemical processes similar to those in use to-day.

The scarcity of wood in Egypt led to the invention of various substitutes. One common substitute was a kind of papier mâché. This was manufactured out of linen, wood or vegetable pulp and various kinds of paste. When it was used for art work the molded forms were covered with lacquer or various kinds of stucco. Very beautiful objects were manufactured from these substances, which indicate that the artists possessed a wide practical knowledge of physical and chemical principles.

Chemical knowledge was also well shown in their manufacture of glass. They excelled in this industry. All kinds of glass were made and decorated by staining and glazing. The glassmakers were able to imitate precious stones in glass and their glass-bead and enamel work has never been excelled. Some modern chemists express the opinion that glass making was carried to a greater degree of perfection in Egypt than any modern nation has attained.