The Earth As Modified By Human Action Part 3

IMPORTANCE OF PHYSICAL CONSERVATION, AND RESTORATION.

Comparatively short as is the period through which the colonization of foreign lands by European emigrants extends, great and, it is to be feared, sometimes irreparable injury has already been done in the various processes by which man seeks to subjugate the virgin earth; and many provinces, first trodden by the h.o.m.o sapiens Europae within the last two centuries, begin to show signs of that melancholy dilapidation which is now driving so many of the peasantry of Europe from their native hearths. It is evidently a matter of great moment, not only to the population of the states where these symptoms are manifesting themselves, but to the general interests of humanity, that this decay should be arrested, and that the future operations of rural husbandry and of forest industry, in districts yet remaining substantially in their native condition, should be so conducted as to prevent the widespread mischiefs which have been elsewhere produced by thoughtless or wanton destruction of the natural safeguards of the soil. This can be done only by the diffusion of knowledge on this subject among the cla.s.ses that, in earlier days, subdued and tilled ground in which they had no vested rights, but who, in our time, own their woods, their pastures, and their ploughlands as a perpetual possession for them and theirs, and have, therefore, a strong interest in the protection of their domain against deterioration.

PHYSICAL RESTORATION.

Many circ.u.mstances conspire to invest with great present interest the questions: how far man can permanently modify and ameliorate those physical conditions of terrestrial surface and climate on which his material welfare depends; how far he can compensate, arrest, or r.e.t.a.r.d the deterioration which many of his agricultural and industrial processes tend to produce; and how far he can restore fertility and salubrity to soil which his follies or his crimes have made barren or pestilential. Among these circ.u.mstances, the most prominent, perhaps, is the necessity of providing new homes for a European population which is increasing more rapidly than its means of subsistence, new physical comforts for cla.s.ses of the people that have now become too much enlightened and have imbibed too much culture to submit to a longer deprivation of a share in the material enjoyments which the privileged ranks have hitherto monopolized.

To supply new hives for the emigrant swarms, there are, first, the vast unoccupied prairies and forests of America, of Australia, and of many other great oceanic islands, the spa.r.s.ely inhabited and still unexhausted soils of Southern and even Central Africa, and, finally, the impoverished and half-depopulated sh.o.r.es of the Mediterranean, and the interior of Asia Minor and the farther East. To furnish to those who shall remain after emigration shall have conveniently reduced the too dense population of many European states, those means of sensuous and of intellectual well-being which are styled "artificial wants" when demanded by the humble and the poor, but are admitted to be "necessaries" when claimed by the n.o.ble and the rich, the soil must be stimulated to its highest powers of production, and man's utmost ingenuity and energy must be tasked to renovate a nature drained, by his improvidence, of fountains which a wise economy would have made plenteous and perennial sources of beauty, health, and wealth.

In those yet virgin lands which the progress of modern discovery in both hemispheres has brought and is still bringing to the knowledge and control of civilized man, not much improvement of great physical conditions is to be looked for. The proportion of forest is indeed to be considerably reduced, superfluous waters to be drawn off, and routes of internal communication to be constructed; but the primitive geographical and climatic features of these countries ought to be, as far as possible, retained.

In reclaiming and reoccupying lands laid waste by human improvidence or malice, and abandoned by man, or occupied only by a nomade or thinly scattered population, the task of the pioneer settler is of a very different character. He is to become a co-worker with nature in the reconstruction of the damaged fabric which the negligence or the wantonness of former lodgers has rendered untenantable. He must aid her in reclothing the mountain slopes with forests and vegetable mould, thereby restoring the fountains which she provided to water them; in checking the devastating fury of torrents, and bringing back the surface drainage to its primitive narrow channels; and in drying deadly mora.s.ses by opening the natural sluices which have been choked up, and cutting new ca.n.a.ls for drawing off their stagnant waters. He must thus, on the one hand, create new reservoirs, and, on the other, remove mischievous acc.u.mulations of moisture, thereby equalizing and regulating the sources of atmospheric humidity and of flowing water, both which are so essential to all vegetable growth, and, of course, to human and lower animal life.

I have remarked that the effects of human action on the forms of the earth's surface could not always be distinguished from those resulting from geological causes, and there is also much uncertainty in respect to the precise influence of the clearing and cultivating of the ground, and of other rural operations, upon climate. It is disputed whether either the mean or the extremes of temperature, the periods of the seasons, or the amount or distribution of precipitation and of evaporation, in any country whose annals are known, have undergone any change during the historical period. It is, indeed, as has been already observed, impossible to doubt that many of the operations of the pioneer settler TEND to produce great modifications in atmospheric humidity, temperature, and electricity; but we are at present unable to determine how far one set of effects is neutralized by another, or compensated by unknown agencies. This question scientific research is inadequate to solve, for want of the necessary data; but well conducted observation, in regions now first brought under the occupation of man, combined with such historical evidence as still exists, may be expected at no distant period to throw much light on this subject.

Australia and New Zealand are, perhaps, the countries from which we have a right to expect the fullest elucidation of these difficult and disputable problems. Their colonization did not commence until the physical sciences had become matter of utmost universal attention, and is, indeed, so recent that the memory of living men embraces the princ.i.p.al epochs of their history; the peculiarities of their fauna, their flora, and their geology are such as to have excited for them the liveliest interest of the votaries of natural science; their mines have given their people the necessary wealth for procuring the means of instrumental observation, and the leisure required for the pursuit of scientific research; and large tracts of virgin forest and natural meadows are rapidly pa.s.sing under the control of civilized man. Here, then, exist greater facilities and stronger motives for the careful study of the topics in question than have ever been found combined in any other theatre of European colonization.

In North America, the change from the natural to the artificial condition of terrestrial surface began about the period when the most important instruments of meteorological observation were invented. The first settlers in the territory now const.i.tuting the United States and the British American provinces had other things to do than to tabulate barometrical and thermometrical readings, but there remain some interesting physical records from the early days of the colonies, [Footnote: The Travels of Dr. Dwight, president of Yale College, which embody the results of his personal observations, and of his inquiries among the early settlers, in his vacation excursions in the Northern States of the American Union, though presenting few instrumental measurements or tabulated results, are of value for the powers of observation they exhibit, and for the sound common sense with which many natural phenomena, such for instance as the formation of the river meadows, called "intervales," in New England, are explained. They present a true and interesting picture of physical conditions, many of which have long ceased to exist in the theatre of his researches, and of which few other records are extant.] and there is still an immense extent of North American soil where the industry and the folly of man have as yet produced little appreciable change. Here, too, with the present increased facilities for scientific observation, the future effects, direct a contingent, of man's labors, can be measured, and such precautions taken in those rural processes which we call improvements, as to mitigate evils, perhaps, in some degree, inseparable from every attempt to control the action of natural laws.

In order to arrive at safe conclusions, we must first obtain a more exact knowledge of the topography, and of the present superficial and climatic condition of countries where the natural surface is as yet more or less unbroken. This can only be accomplished by accurate surveys, and by a great mutiplication of the points of meteorological registry, [Footnote: The general law of tempeture is that it decreases as we ascend. But in hilly areas the law is reversed in cold, still weather, the cold air descending, by reason of its greater gravity, into the valleys. If there be wind enough however, to produce a disturbance and intermixture of higher and lower atmospheric strata, this exception to the general law does not take place. These facts have long been familiar to the common people of Switzerland and of New England, but their importance has not been sufficiently taken into account in the discussion of meterological observations. The descent of the cold air and the rise of the warm effect the relative temperatures of hills and valleys to a much greater extent that has been usually supposed. A gentleman well known to me kept a thermometrical record for nearly a half century in a New England county town, at an elevation of at least 1,5000 feet above the sea. During these years his thermometer never fell lower that 26 degrees Farrenheit, while at the shire town of the county, situated in a basin thousand feet lower, and only tem miles distant, as well as at other points in similar positions, the mercury froze several times in the same period] already so numerous; and as, moreover, considerable changes in the proportion of forest and of cultivated land, or of dry and wholly or partially submerged surface, will often take place within brief periods, it is highly desirable that the attention of observers, in whose neighborhood the clearing of the soil, of the drainage of lakes and swamps, or other great works of rural improvement, are going on or meditated, should be especially drawn not only to revolutions in atmospheric tempeture and precipitation, but to the more easily ascertained and perhaps more important local changes produced by these operations in the temperature and the hygrometric state of the superficial strata of the earth, and in its spontaneous vegetable and animal products.

The rapid extension of railroads, which now everywhere keep pace with, and sometimes even precede, the occupation of new soil for agricultural purposes, furnishes great facilities for enlarging our knowledge of the topography of the territory they traverse, because their cuttings reveal the composition and general structure of surface, and the inclination and elevation of their lines const.i.tute known hypsometrical sections, which give numerous points of departure for the measurement of higher and lower stations, and of course for determining the relief and depression of surface, the slope of the beds of watercourses, and many other not less important questions. [Footnote: Railroad surveys must be received with great caution where any motive exists for COOKING them.

Capitalists are shy of investments in roads with steep grades, and of course it is important to make a fair show of facilities in obtaining funds for new routes. Joint-stock companies have no souls; their managers, in general, no consciences. Cases can be cited where engineers and directors of railroads, with long grades above one hundred foot to the mile, have regularly sworn in their annual reports, for years in succession, that there were no grades upon their routes exceeding half that elevation. In fact, every person conversant with the history of these enterprises knows that in their public statements falsehood is the rule, truth the exception.

What I am about to remark is not exactly relevant to my subject; but it is hard to "get the floor" in the world's great debating society, and when a speaker who has anything to say once finds access to the public ear, he must make the must of his opportunity, without inquiring too nicely whether his observations are "in order." I shall harm no honest man by endeavoring, as I have often done elsewhere, to excite the attention of thinking and conscientious men to the dangers which threaten the great moral and even political interests of Christendom, from the unscrupulousness of the private a.s.sociations that now control the monetary affairs, and regulate the transit of persons and property, in almost every civilized country. More than one American State is literally governed by unprincipled corporations, which not only defy the legislative power, but have, too often, corrupted even the administration of justice. The tremendous power of these a.s.sociations is due not merely to pecuniary corruption, but partly to an old legal superst.i.tion--fostered by the decision of the Supreme Court of the United States in the famous Dartmouth College case--in regard to the sacredness of corporate prerogatives. There is no good reason why private rights derived from G.o.d and the very const.i.tution of society should be less respected than privileges granted by legislatures. It should never be forgotten that no privilege can be a right, and legislative bodies ought never to make a grant to a corporation, without express reservation of what many sound jurists now hold to be involved in the very nature of such grants, the power of revocation. Similar evils have become almost equally rife in England, and on the Continent; and I believe the decay of commercial morality, and of the sense of all higher obligations than those of a pecuniary nature, on both sides of the Atlantic, is to be ascribed more to the influence of joint-stock banks and manufacturing and railway companies, to the workings, in short, of what is called the principle of "a.s.sociate action," than to any other one cause of demoralization.

The apophthegm, "the world is governed too much," though unhappily too truly spoken of many countries--and perhaps, in some aspects, true of all--has done much mischief whenever it has been too unconditionally accepted as a political axiom. The popular apprehension of being over-governed, and, I am afraid, more emphatically the fear of being over-taxed, has had much to do with the general abandonment of certain governmental duties by the ruling powers of most modern states. It is theoretically the duty of government to provide all those public facilities of intercommunication and commerce, which are essential to the prosperity of civilized commonwealths, but which individual means are inadequate to furnish, and for the due administration of which individual guarantees are insufficient. Hence public roads, ca.n.a.ls, railroads, postal communications, the circulating medium of exchange whether metallic or representative, armies, navies, being all matters in which the nation at large has a vastly deeper interest than any private a.s.sociation can have, ought legitimately to be constructed and provided only by that which is the visible personification and embodiment of the nation, namely, its legislative head. No doubt the organization and management of those insitutions by government are liable, as are all things human, to great abuses. The multiplication of public placeholders, which they imply, is a serious evil. But the corruption thus engendered, foul as it is, does not strike so deep as the rottenness of private corporations; and official rank, position, and duty have, in practice, proved better securities for fidelity and pecuniary integrity in the conduct of the interests in question, than the suretyships of private corporate agents, whose bondsmen so often fail or abscond before their princ.i.p.al is detected. Many theoretical statesmen have thought that voluntary a.s.sociations for strictly pecuniary and industrial purposes, and for the construction and control of public works, might furnish, in democratic countries, a compensation for the small and doubtful advantages, and at the same time secure an exemption from the great and certain evils, of aristocratic inst.i.tutions. The example of the American States shows that private corporations--whose rule of action is the interest of the a.s.sociation, not the conscience of the individual--though composed of ultra-democratic elements, may become most dangerous enemies to rational liberty, to the moral interests of the commonwealth, to the purity of legislation and of judicial action, and to the sacredness of private rights.]

The geological, hydrographical, and topographical surveys, which almost every general and even local government of the civilized world is carrying on, are making yet more important contributions to our stock of geographical and general physical knowledge, and, within a comparatively short s.p.a.ce, there will be an acc.u.mulation of well established constant and historical facts, from which we can safely reason upon all the relations of action and reaction between man and external nature.

But we are, even now, breaking up the floor and wainscoting and doors and window frames of our dwelling, for fuel to warm our bodies and to seethe our pottage, and the world cannot afford to wait till the slow and sure progress of exact science has taught it a better economy. Many practical lessons have been learned by the common observation of unschooled men; and the teachings of simple experience, on topics where natural philosophy has scarcely yet spoken, are not to be despised.

In these humble pages, which do not in the least aspire to rank among scientific expositions of the laws of nature, I shall attempt to give the most important practical conclusions suggested by the history of man's efforts to replenish the earth and subdue it; and I shall aim to support those conclusions by such facts and ill.u.s.trations only as address themselves to the understanding of every intelligent reader, and as are to be found recorded in works capable of profitable perusal, or at least consultation, by persons who have not enjoyed a special scientific training.

CHAPTER II.

TRANSFER, MODIFICATION, AND EXTIRPATION OF VEGETABLE AND OF ANIMAL SPECIES.

Modern geography takes account of organic life--Geographical importance of plants--Origin of domestic vegetables-Transfer of vegetable life--Objects of modern commerce-Foreign plants, how introduced--Vegetable power of accommodation--Agricultural products of the United States--Useful American plants grown in Europe--Extirpation of vegetables--Animal life as a geological and geographical agency--Origin and transfer of domestic quadrupeds--Extirpation of wild quadrupeds--Large marine animals relatively unimportant in geography--Introduction and breeding of fish--Destruction of fish--Geographical importance of birds--Introduction of birds--Destruction of birds--Utility and destruction of reptiles--Utility of insects and worms--Injury to the forest by insects--Introduction of insects--Destruction of insects--Minute organisms.

MODERN GEOGRAPHY EMBRACES ORGANIC LIFE.

It was a narrow view of geography which confined that science to delineation of terrestrial surface and outline, and to description of the relative position and magnitude of land and water. In its improved form it embraces not only the globe itself and the atmosphere which bathes it, but the living things which vegetate or move upon it, the varied influences they exert upon each other, the reciprocal action and reaction between them and the earth they inhabit. Even if the end of geographical studies were only to obtain a knowledge of the external forms of the mineral and fluid ma.s.ses which const.i.tute the globe, it would still be necessary to take into account the element of life; for every plant, every animal, is a geographical agency, man a destructive, vegetables, and in some cases even wild beasts, restorative powers. The rushing waters sweep down earth from the uplands; in the first moment of repose, vegetation seeks to reestablish itself on the bared surface, and, by the slow deposit of its decaying products, to raise again the soil which the torrent lhad lowered. So important an element of reconstruction in this, that it has been seriously questioned whether, upon the whole, vegetation does not contribute as much to elevate, as the waters to depress, the level of the surface.

Whenever man has transported a plant from its native habitat to a new soil, he has introduced a new geographical force to act upon it, and this generally at the expense of some indigenous growth which the foreign vegetable has supplanted. The new and the old plants are rarely the equivalents of each other, and the subst.i.tution of an exotic for a native tree, shrub, or gra.s.s, increases or diminishes the relative importance of the vegetable element in thegeography of the country to which it is removed. Further, man sows that he may reap. The products of agricultural industry are not suffered to rot upon the ground, and thus raise it by an annual stratum of new mould. They are gathered, transported to greater or less distances, and after they have served their uses in human economy, they enter, on the final decomposition of their elements, into new combinations, and are only in smnall proportion returned to the soil on which they grew. The roots of the gra.s.ses, and of many other cultivated plants, however, usually remain and decay in the earth, and contribute to raise its surface, though certainly not in the same degree as the forest.

The smaller vegetables which have taken the place of trees unquestionably perform many of the same functions. They radiate heat, they absorb gases, and exhale uncombined gases and watery vapor, and consequently act upon the chemical const.i.tution and hygrometrical condition of the air, their roots penetrate the earth to greater depths than is commonly supposed, and form an inextricable labyrinth of filaments which bind the soil together and prevent its erosion by water.

The broad-leaved annuals and perennials, too, shade the ground, and prevent the evaporation of moisture from its surface by wind and sun.

[Footnote: It is impossible to say how far the abstraction of water from the earth by broad-leaved field and garden plants--such as maize, the gourd family, the cabbage, &c.--is compensated by the condensation of dew, which sometimes pours from them in a stream, by the exhalation of aqueous vapor from their leaves, which is directly absorbed by the ground, and by the shelter they afford the soil from sun and wind, thus preventing evaporation. American farmers often say that after the leaves of Indian corn are large enough to "shade the ground," there is little danger that the plants will suffer from drought; but it is probable that the comparative security of the fields from this evil is in port due to the fact that, at thin period of growth, the roots penetrate down to a permanently humid stratum of soil, and draw from it the moisture they require. Stirring the ground between the rows of maize with a light harrow or cultivator, in very dry seasons, is often recommended as a preventive of injury by drought. It would seem, indeed, that loosening and turning over the surface earth might aggravate the evil by promoting the evaporation of the little remaining moisture; but the practice is founded partly on the belief that the hygroscopicity of the soil is increased by it to such a degree that it gains more by absorption than it loses by evaporation, and partly on the doctrine that to admit air to the rootlets, or at least to the earth near them, is to supply directly elements of vegetable growth.] At a certain stage of growth, gra.s.s land is probably a more energetic evaporator and refrigerator than even the forest, but this powerful action is exerted, in its full intensity, for a comparatively short time only, while trees continue such functions, with unabated vigor, for many months in succession. Upon the whole, it seems quite certain, that no cultivated ground is as efficient in tempering climatic extremes, or in conservation of geographical surface and outline, as is the soil which nature herself has planted.

ORIGIN OF DOMESTIC PLANTS.

One of the most important questions connected with our subject is: how far we are to regard our cereal grains, our esculent bulbs and roots, and the multiplied tree fruits of our gardens, as artificially modified and improved forms of wild, self-propagating vegetation. The narratives of botanical travellers have often announced the discovery of the original form and habitat of domesticated plants, and scientific journals have described the experiments by which the ident.i.ty of particular wild and cultivated vegetables has been thought to be established. It is confidently affirmed that maize and the potato--which we must suppose to have been first cultivated at a much later period than the breadstuffs and most other esculent vegetables of Europe and the East--are found wild and self-propagating in Spanish America, though in forms not recognizable by the common observer as identical with the familiar corn and tuber of modern agriculture. It was lately a.s.serted, upon what seemed very strong evidence, that the Aegilops ovata, a plant growing wild in Southern France, had been actually converted into common wheat; but, upon a repet.i.tion of the experiments, later observers have declared that the apparent change was only a case of temporary hybridation or fecundation by the pollen of true wheat, and that the gra.s.s alleged to be transformed into wheat could not be perpetuated as such from its own seed.

The very great modifications which cultivated plants are constantly undergoing under our eyes, and the numerous varieties and races which spring up among them, certainly countenance the doctrine, that every domesticated vegetable, however dependent upon human care for growth and propagation in its present form, may have been really derived, by a long Succession of changes, from some wild plant not now perhaps much resembling it. [Footnote: What is the possible limit of such changes, we do not know, but they may doubtless be carriad vastly beyond what experience has yet shown to be practicable. Civilized man has experimented little on wild plants, and especially on forest trees. He has indeed improved the fruit, and developed new varieties, of the chestnut, by cultivation, and it is observed that our American forest-tree nuts and berries, such as the b.u.t.ternut and thewild mulberry, become larger and better flavored in a single generation by planting and training. (Bryant, Forest Trees, 1871, pp. 99, 115.) Why should not the industry and ingenuity which have wrought such wonders in our horticulture produce a.n.a.logous results when applied to the cultivation and amelioration of larger vegetables Might not, for instance, the ivory nut, the fruit of the Phytelephas macrocarpa, possibly be so increased in size as to serve nearly all the purposes of animal ivory now becoming so scarce Might not the various milk-producing trees become, by cultivation, a really important source of nutriment to the inhabitants of warm climates In short, there is room to hope incalculable advantage from the exercise of human skill in the improvement of yet untamed forms of vegetable life.] But it is, in every case, a question of evidence.

The only satisfactory proof that a given wild plant is identical with a given garden or field vegetable, is the test of experiment, the actual growing of the one from the seed of the other, or the conversion of the one into the other by transplantation and change of conditions.

[Footnote: The poisonous wild parsnip of New England has been often a.s.serted to be convertible into the common garden parsnip by cultivation, or rather to be the same vegetable growing under different conditions, and it is said to be deprived of its deleterious qualities simply by an increased luxuriance of growth in rich, tilled earth. Wild medicinal plants, so important in the rustic materia medica of New England--such as pennyroyal, for example--are generally much less aromatic and powerful when cultivated in gardens than when self-sown on meagre soils. On the other hand, the cinchona, lately introduced from South America into British India and carefully cultivated there, is found to be richer in quinine than the American tree.]

It is hardly contended that any of the cereals or other plants important as human aliment, or as objects of agricultural industry, exist and propagate themselves uncultivated in the same form and with the same properties as when sown and reared by human art. [Footnote: Some recent observations of Wetzatein are worthy of special notice. "The soil of the Hauran," he remarks, "produces, in its primitive condition, much wild rye, which is not known as a cultivated plant in Syria, and much wild barley and oats. These cereals precisely resemble the corresponding cultivated plants in leaf, ear, size, and height of straw, but their grains are sensibly flatter and poorer in flour."--Reisebericht uber Hauran und die Trachenen, p. 40.

Some of the cereals are, to a certain extent, self-propagating in the soil and climate of California. "VOLUNTEER crops are grown from the seed which falls out in harvesting. Barley has been known to volunteer five crops in succession."--Prayer-Frowd, Six Months in California, p. 189.]

In fact, the cases are rare where the ident.i.ty of a wild with a domesticated plant is considered by the best authorities as conclusively established, and we are warranted in affirming of but few of the latter, as a historically known or experimentally proved fact, that they ever did exist, or could exist, independently of man. [Footnote: This remark is much less applicable to fruit trees than to garden vegetables and the cerealia. The wild orange of Florida, though once considered indigenous, is now generally thought by botanists to be descended from the European orange introduced by the early colonists. On the wild apple trees of Ma.s.sachusetts see an interesting chapter in Th.o.r.eau, Excursions. The fig and the olive are found growing wild in every country where those trees are cultivated The wild fig differs from the domesticated in its habits, its season of fructification, and its insect population, but is, I believe, not specifically distinguishable from the garden fig, though I do not know that it is reclaimable by cultivation. The wild olive, which is so abundant in the Tuscan Maremma, produces good fruit without further care, when thinned out and freed from the shade of other trees, and is particularly suited for grafting. See Salvagnoli, Memorie sulle Maremme, pp. 63-73. The olive is indigenous in Syria and in the Punjaub, and forms vast forests in the Himalayas at from 1,400 to 2,100 feet above the level of the sea.--Cleghorn, Memoir on the Timber procured from the Indus, etc., pp. 8-15. Fraas, Klima und Pfanzenwelt in der Zeit, pp. 35-38, gives, upon the authority of Link and other botanical writers, a lift of the native habitats of most cereals and of many fruits, or at least of localities where those plants are said to be now found wild; but the data do not appear to rest, in general, upon very trustworthy evidence. Theoretically, there can be little doubt that all our cultivated plants are modified forms of spontaneous vegetation, though the connection is not historically shown, nor are we able to say that the originals of some domesticated vegetables may not be now extinct and unrepresented in the existing wild flora. See, on this subject, Humboldt, Ansichten der Natur, i., pp. 208, 209.

The Adams of modern botany and zoology have been put to hard shifts in finding names for the multiplied organisms which the Creator has brought before them, "to see what they would call them;" and naturalists and philosophers have shown much moral courage in setting at naught the law of philology in the coinage of uncouth words to express scientific Ideas. It is much to be wished that some bold neologist would devise English technical equivalents for the German verwildert, run-wild, and veredelt, improved by cultivation.]

Transfer of Vegetable Life.

It belongs to vegetable and animal geography, which are almost sciences of themselves, to point out in detail what man has done to change the distribution of plants and of animated life and to revolutionize the aspect of organic nature; but some of the more important facts bearing on the first branch of this subject may pertinently be introduced here.

Most of the cereal grains, the pulse, the edible roots, the tree fruits, and other important forms of esculent vegetation grown in Europe and the United States are believed, and--if the testimony of Pliny and other ancient naturalists is to be depended upon--many of them are historically known, to have originated in the temperate climates of Asia. The agriculture of even so old a country as Egypt has been almost completely revolutionized by the introduction of foreign plants, within the historical period. "With the exception of wheat," says Hehn, "the Nile valley now yields only new products, cotton, rice, sugar, indigo, sorghum, dates," being all unknown to its most ancient rural husbandry.

[Footnote: On these points see the learned work of Hehn, Kultur.

Pflanzen und Thiere in ihrem Uebergang aus Asien, 1870. On the migration of plants generally, see Lyell, Principles of Geology, 10th ed., vol.

ii., c.] The wine grape has been thought to be truly indigenous only in the regions bordering on the eastern end of the Black Sea, where it now, particularly on the banks of the Rion, the ancient Phasis, propagates itself spontaneously, and grows with unexampled luxuriance. [Footnote: The vine-wood planks of the ancient great door of the cathedral at Ravenna, which measured thirteen feet in length by a foot and a quarter in width, are traditionally said to have boon brought from the Black Sea, by way of Constantinople, about the eleventh or twelfth century.

Vines of such dimension are now very rarely found in any other part of the East, and, though I have taken some pains on the subject, I never found in Syria or in Turkey a vine stock exceeding six inches in diameter, bark excluded. Schulz, however, saw at Beitschin, near Ptolemais, a vine measuring eighteen inches in diameter. Strabo speaks of vine-stocks in Margiana (Khorasan) of such dimension that two men, with outstretched arms, could scarcely embrace them. See Strabo, ed.

Casaubon, pp. 78, 516, 826. Statues of vine wood are mentioned by ancient writers. Very large vine-stems are not common in Italy, but the vine-wood panels of the door of the chapter-hall of the church of St.

John at Saluzzo are not less than ten inches in width, and I observed not long since, in a garden at Pie di Mulera, a vine stock with a circ.u.mference of thirty inches.] But some species of the vine seem native to Europe, and many varieties of grape have been too long known as common to every part of the United States to admit of the supposition that they were introduced by European colonists. [Footnote: The Northmen who--as I think it has been indisputably established by Professor Rafn of Copenhagen--visited the coast of Ma.s.sachusetts about theyear 1000, found grapes growing there in profusion, and the wild vine still flourishes in great variety and abundance in the southeastern counties of that State. The townships in the vicinity of the Dighton rock, supposed by many--with whom, however, I am sorry I cannot agree--to bear a Scandinavian inscription, abound in wild vines. According to Laudonniere, Histoire Notable de la Florida, reprint, Paris, 1853, p 5, the French navigators in 1562 found in that peninsula "wild vines which climb the trees and produce good grapes."]

OBJECTS OF MODERN COMMERCE.

It is an interesting fact that the commerce--or at least the maritime carrying trade--and the agricultural and mechanical industry of the world are, in very large proportion, dependent on vegetable and animal products little or not at all known to ancient Greek, Roman, and Jewish civilization. In many instances, the chief supply of these articles comes from countries to which they are probably indigenous, and where they are still almost exclusively grown; but in most cases, the plants or animals from which they are derived have been introduced by man into regions now remarkable for their successful cultivation, and that, too, in comparatively recent times, or, in other words, within two or three centuries.

Something of detail on this subject cannot, I think, fail to prove interesting. Pliny mentions about thirty or forty oils as known to the ancients, of which only olive, sesame, rape seed and walnut oil--for except in one or two doubtful pa.s.sages I find in this author no notice of linseed oil--appear to have been used in such quant.i.ties as to have had any serious importance in the carrying trade. At the present time, the new oils, linseed oil, the oil of the whale and other largeo marine animals, petroleum--of which the total consumption of the world in 1871 is estimated at 6,000,000 barrels, the port of Philadelphia alone exporting 56,000,000 gallons in that year--palm-oil recently introduced into commerce, and now imported into England from the coast of Africa at the rate of forty or fifty thousand tuns a year, these alone undoubtedly give employment to more shipping than the whole commerce of Italy--with the exception of wheat--at the most flourishing period of the Roman empire. [Footnote: A very few years since, the United States had more than six hundred large ships engaged in the whale fishery, and the number of American whalers, in spite of the introduction of many now sources of oils, still amounts to two hundred and fifty.

The city of Rome imported from Sicily, from Africa, and from the Levant, enormous quant.i.ties of grain for gratuitous distribution among the lower cla.s.ses of the capital. The pecuniary value of the gems, the spices, the unguents, the perfumes, the cosmetics and the tissues, which came princ.i.p.ally from the East, was great, but these articles were neither heavy nor bulky and their transportation required but a small amount of shipping. The marbles, the obelisks, the statuary and other objects of art plundered in conquered provinces by Roman generals and governors, the wild animals, such as elephants, rhinoceroses, hippopotami, camelopards and the larger beasts of prey imported for slaughter at the public games, and the prisoners captured in foreign wars and brought to Italy for sale as slaves or butchery as gladiators, furnished employment for much more tonnage than all the legitimate commerce of the empire, with the possible exception of wheat. Independently of the direct testimony of Latin authors, the Greek statuary, the Egyptian obelisks, and the vast quant.i.ties of foreign marbles, granite, parphyry, basalt, and other stones used in sculpture and in architecture, which have been found in the remains of ancient Rome, show that the Imperial capital must have employed an immense amount of tonnage in the importation of heavy articles for which there could have been no return freight, unless in the way of military transportation. Some of the Egyptian obelisks at Rome weigh upwards of four hundred tons, and many of the red granite columns from the same country must have exceeded one hundred tons. Greek and African marbles were largely used not only for columns, contablatures, and solid walls, but for casing the exterior and veneering the interior of public and private buildings. Scaurus imported, for the scene alone of a temporary theatre designed to stand scarcely for a month, three hundred and sixty columns, which were disposed in three tiers, the lower range being forty-two feet in height--See Pliny, Nat. Hist., Lib. x.x.xvi. Italy produced very little for export, and her importations, when not consisting of booty, were chiefly paid for in coin which was princ.i.p.ally either the spoil of war or the fruit of official extortion.]

England imports annually about 600,000 tons of sugar, 100,000 tons of jute, and about the same quant.i.ty of esparto, six million tons of cotton, of which the value of $30,000,000 is exported again in the form of manufactured, goods--including, by a strange industrial revolution, a large amount of cotton yarn and cotton tissues sent to India and directly or indirectly paid for by raw cotton to be manufactured in England--30,000 tons of tobacco, from 100,000 to 350,000 tons of guano, hundreds of thousands of tons of tea, coffee, cacao, caoutchone, gutta-percha and numerous other important articles of trade wholly unknown, as objects of commerce, to the ancient European world; and this immense importation is balanced by a corresponding amount of exportation, not consisting, however, by any means, exclusively of articles new to commerce. [Footnote: Many of these articles would undoubtedly have been made known to the Greeks and Romans and have figured in their commerce, but for the slowness and costliness of ancient navigation, which, in the seas familiar to them, was suspended for a full third of the year from the inability of their vessels to cope with winter weather. The present speed and economy of transportation have wrought and are still working strange commercial and industrial revolutions. Algeria now supplies Northern Germany with fresh cauliflowers, and in the early spring the market-gardeners of Naples find it more profitable to send their first fruits to St. Petersburg than to furnish them to Florence and Rome.]

FOREIGN PLANTS, HOW INTRODUCED.