Nature has no unit of magnitude by which she measures her works. Man takes his standards of dimension from himself. The hair's breadth was his minimum until the microscope told him that there are animated creatures to which one of the hairs of his head is a larger cylinder than is the trunk of the giant California sequoia to him. He borrows his inch from the breadth of his thumb, his palm and span from the width of his hand and the spread of his fingers, his foot from the length of the organ so named; his cubit is the distance from the tip of his middle finger to his elbow, and his fathom is the space he can measure with his outstretched arms. [Footnote: The French metrical system seems destined to be adopted throughout the civilized world. It is indeed recommended by great advantages, but it is very doubtful whether they are not more than counterbalanced by the selection of too large a unit of measure, and by the inherent intractability of all decimal systems with reference to fractional divisions. The experience of the whole world has established the superior convenience of a smaller unit, such as the braccio, the cubit, the foot, and the palm or span, and in practical life every man finds that he haa much more frequent occasion to use a fraction than a multiple of the metre. Of course, he must constantly employ numbers expressive of several centimetres or millimetres instend of the name of a single smaller unit than the metre. Besides, the metre is not divisible into twelfths, eighths, sixths, or thirds, or the multiples of any of these proportions, two of which at least—the eighth and the third—are of as frequent use as any other fractions. The adoption of a fourth of the earth's circumference as a base for the new measures was itself a departure from the decimal system. Had the Commissioners taken the entire circumference as a base, and divided it into 100,000,000 instead of 10,000,000 parts, we should have had a unit of about sixteen inches, which, as a compromise between the foot and the cubit, would have been much better adapted to universal use than so large a unit as the metre.] To a being who instinctively finds the standard of all magnitudes in his own material frame, all objects exceeding his own dimensions are absolutely great, all falling short of them absolutely small. Hence we habitually regard the whale and the elephant as essentially large and therefore important creatures, the animalcule as an essentially small and therefore unimportant organism. But no geological formation owes its origin to the labors or the remains of the huge mammal, while the animalcule composes, or has furnished, the substance of strata thousands of feet in thickness, and extending, in unbroken beds, over many degrees of terrestrial surface. If man is destined to inhabit the earth much longer, and to advance in natural knowledge with the rapidity which has marked his progress in physical science for the last two or three centuries, he will learn to put a wiser estimate on the works of creation, and will derive not only great instruction from studying the ways of nature in her obscurest, humblest walks, but great material advantage from stimulating her productive energies in provinces of her empire hitherto regarded as forever inaccessible, utterly barren. [Footnote: The fermentation of liquids, and in many cases the decomposition of semi-solids, formerly supposed to be owing purely to chemical action, are now ascribed by many chemists to vital processes of living minute organisms, both vegetable and animal, and consequently to physiological as well as to chemical forces. Even alcohol is stated to be an animal product. The whole subject of animalcular, or rather minute organic, life, has assumed a now and startling importance from the recent researches of naturalists and physiologists, in the agency of such life, vegetable or animal, in exciting and communicating contagious diseases, and it is extremely probable that what are vaguely called germs, to whichever of the organic kingdoms they may be assigned, creatures inhabiting various media, and capable of propagating their kind and rapidly multiplying, are the true seeds of infection and death in the maladies now called zymotic, as well perhaps as in many others.
The literature of this subject is now very voluminous. For observations with high microscopic power on this subject, see Beale, Disease Germs, their supposed Nature, and Disease Germs, their real Nature, both published in London in 1870.
The increased frequency of typhoidal, zymotic, and malarious diseases in some parts of the United States, and the now common occurrence of some of them in districts where they were unknown forty years ago, are startling facts, and it is a very interesting question how far man's acts or neglects may have occasioned the change. See Third Anual Report of Massachusetts State Board of Health for 1873. The causes and remedies of the insalubrity of Rome and its environs have been for some time the object of careful investigation, and many valuable reports have been published on the subject. Among the most recent of these are: Relazione sulle condizioni agrarie ed igieniche della Campagna di Roma, per Raffaele Pareto; Cenni Storici sulla questione dell' Agro Romano di G. Guerzoni; Cenni sulle condizioni Fisico-economiche di Roma per F. Giordano; and a very important paper in the journal Lo Sperimentale for 1870, by Dr. D. Pantaleoni.
There are climates, parts of California, for instance, where the flesh of dead animals, freely exposed, shows no tendency to putrefaction but dries up and may be almost indefinitely preserved in this condition. Is this owing to the absence of destructive animalcular life in such localities, and has man any agency in the introduction and naturalization of these organisms in regions previously not infested by them ]
CHAPTER III.
THE WOODS.
The habitable earth originally wooded—General meteorological influence of the forest—Electrical action of trees—Chemical influence of woods—Trees as protection against malaria—Trees as shelter to ground to the leeward—Influence of the forest as inorganic on temperature—Thermometrical action of trees as organic—Total influence of the forest on temperature—Influence of forests as inorganic on humidity of air and earth—Influence as organic—Balance of conflicting influences—Influence of woods on precipitation—Total climatic action of the forest—Influence of the forest on humidity of soil—The forest in winter—Summer rain, importance of—Influence of the forest on the flow of springs—Influence of the forest on inundations and torrents—Destructive action of torrents—Floods of the Ardeche—Excavation by torrents—Extinction of torrents—Crushing force of torrents—Transporting power of water—The Po and its deposits—Mountain slides—Forest as protection against avalanches—Minor uses of the forest—Small forest plants and vitality of seeds—Locusts do not breed in forests—General functions of forest—General consequences of destruction of—Due proportion of woodland—Proportion of woodland in European countries—Forests of Great Britain—Forests of France—Forests of Italy—Forests of Germany—Forests of United States—American forest trees—European and American forest trees compared—The forest does not furnish food for man—First removal of the forest—Principal causes of destruction of forest—Destruction and protection of forests by governments—Royal forests and game-laws—Effects of the French revolution—Increased demand for lumber—Effects of burning forest—Floating of timber—Restoration of the forest—Economy of the forest—Forest legislation—Plantation of forests in America—Financial results of forest plantations—Instability of American life.
The Habitable Earth originally Wooded.
There is good reason to believe that the surface of the habitable earth, in all the climates and regions which have been the abodes of dense and civilized populations, was, with few exceptions, already covered with a forest growth when it first became the home of man. This we infer from the extensive vegetable remains—trunks, branches, roots, fruits, seeds, and leaves of trees—so often found in conjunction with works of primitive art, in the boggy soil of districts where no forests appear to have existed within the eras through which written annals reach; from ancient historical records, which prove that large provinces, where the earth has long been wholly bare of trees, were clothed with vast and almost unbroken woods when first made known to Greek and Roman civilization; [Footnote: The recorded evidence in support of the proposition in the text has been collected by L. F. Alfred Maury, in his Histoire des grandes Forets de la Gauls et de l'ancienne France, and by Becquerel, in his important work, Des climats et de l'Influence qu'exercent les Sols boises et non boises, livre ii., chap. i. to iv.
We may rank among historical evidences on this point, if not technically among historical records, old geographical names and terminations etymologically indicating forest or grove, which are so common in many parts of the Eastern Continent now entirely stripped of woods—such as, in Southern Europe, Breuil, Broglio, Brolio, Brolo; in Northern, Bruhl, and the endings -dean, -den, -don, -ham, -holt, -horst, -hurst, -lund, -shaw, -shot, -skog, -skov, -wald, -weald, -wold, -wood.] and from the state of much of North and of South America, as well as of many islands, when they were discovered and colonized by the European race. [Footnote: The island of Madeira, whose noble forests wore devastated by fire not Iong after its colonization by European settlors, takes its name from the Portuguese word tor wood.]