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.