EARTH, AIR, AND WATER IN RELATION TO MAN—HOW MODIFIED BY HIM—RESULTS OF THAT MODIFICATION—ACTION AND REACTION.  
§ 1. The question of acclimation is not confined merely to man’s transfer from one country to another, and to his attempts to accommodate himself to the new locality, to the altered circumstances of his adopted country. As civilized man traverses the earth in search of new abodes, he carries with him the arts of social life, and especially the art of agriculture, by which alone he can exist in congregated masses: agriculture, which forms indeed the very basis of civilization.
Whether we view man as a native of the land or a stranger, he cannot evade this question; for even as a native and as an individual of a race whose presence on the soil he may inhabit precedes the records of authentic history, if he form a portion of civilized society he receives from his ancestors or predecessors a system he is bound to improve, or at least to maintain, so that he shall live and thrive, not as the beasts of the field, but as a member of a civilized people. When a hunting tribe of North American Indians, a horde of Bedouins, or Hottentots or Caffres, a Turcoman family, or a gipsy encampment, a Cape Boer, or an Australian sheep-farmer, sit down by stream, or valley, or lake, they no more influence the soil than a troop of antelopes or buffaloes. Nature’s great processes go on unaffected: they deteriorate, it is true, by respiration, the superincumbent atmosphere, but not more than any equal amount of animal life. This deterioration the wild plants around, sown by nature herself, speedily removes; the oxygen consumed by savage man and the animal life around, equally wild, is speedily renovated by vegetation, and the oxygen they remove from the atmosphere and the carbonic acid they pour into it, rapidly and constantly recover their equilibrium under the influence of vegetation. Thus, neither the earth (soil), air, nor water, is in any way influenced by his presence, nor is he in general affected by these; there is no reciprocal influence for good or bad: he cuts down no forests, grows no wheat, or but little, makes no canals, drains no marsh-lands, poisons no rivers; the refuse of his dwellings, the excreta of such a population, are not sensibly perceived, even if allowed to rot and waste away on the surface—a practice prevalent with most if not all wild and uncultivated people; it rapidly disappears, disintegrated by processes in which the lower forms of animal life take a part. Now, contemplate the picture civilized man presents, and see him in direct antagonism with nature! The plants of nature’s sowing are rudely torn up with the plough and destroyed, the fields are forced to yield crops by which he lives, and what he takes from the soil must, to use the language of chemists, “be restored to it:” the excreta of man and animals, the refuse of dwellings, the deteriorated and poisoned liquids, the products of manufactories, are collected into heaps, to rot on the surface of the soil, before being dug into it; or are thrown into the rivers, to poison, in a certain sense, the waters on which man lives, rendering their banks, if not pestilential, at least most unpleasant as human abodes; canals are dug, vast reservoirs are formed, which in time give rise by mismanagement to fevers, intermittent and others; the minerals of the earth are quarried and placed on the soil, mines are dug, and from them waters are discharged into the neighbouring streams, strongly poisoned with the metallic ores. To imagine that an influence thus affecting earth, air, and water can proceed and increase without affecting human life, can be overcome by habit, does not require to be met by counter-influences originating in the experience and reasoning of man himself, is a supposition which the history of large cities refutes. The influence is reciprocal. When man thus acts on the three elements of nature by which he lives, they react on him, and it is this reaction he is called on to meet and to overcome as best he can. It is a question of reason and experiment—that is, of science and of simple observation; simple observation and experiment taught the native Peruvians the value of guano, for science had at that time no standing on the American continent; and now the chemist steps in and explains why it was that the experiment proved successful. Whether his explanation be satisfactory or not, touches not the question; though proved to be erroneous in a single instance, as it possibly is in regard of this very Peruvian guano, science stands on too secure a basis to require any defence from me.
It is one of the conditions of civilization, that man must everywhere accept the social system within which he lives. Whether a dweller in detached cottages and farm-houses, or congregated into townships and villages; collected in masses, as in towns and cities, his endeavour is to protect his dwelling from all that is offensive and from whatever may prove injurious to the health of himself and family. An ancient adage tells us not to act contrary to nature; but as nature reveals nothing to us, as her intentions can only be read by the lights of science and reason, or science based on observation and experiment, whence human reason draws deductions conformable with its power, so is it most difficult for man to say what is best to be done under all circumstances. When a man builds a cottage, a house, or a palace, after duly attending to the surface-drains, he constructs near his dwelling, sometimes beneath it, a cesspool and a dead-well, the former intended to receive the more solid excreta, the latter the soil-water of the kitchen—the water, in fact, used in the domestic economy of the house. If the dead-well or pit dug to receive the soiled water of the house be sufficiently deep, it filters through the soil, and thus requires no clearing out—if not, it overflows the court or garden, and speedily renders the place uninhabitable. The cesspool, if deep enough and properly secured, remains for many years unknown and unperceived, until filled; it may even be forgotten altogether, and its very existence remain unknown, until disclosed by accident; but whatever be its age or condition, so soon as its contents are exposed to the air, it is found to have continued unaltered; and if spread on the fields, as I have seen done, renders the vicinity for some time unendurable, thus proving the sagacity of the Jewish legislator in his instructions to that people to whom he gave laws and regulations to serve them for all time to come.34
If the adage I have quoted above be true—namely, that we must not act contrary to nature—there is another of the truth of which we feel more assured. It is this: whenever man interferes with nature, he must take the whole matter on himself, and be prepared to meet every contingency. Nature gave us streams and rivers more or less pure, whose banks are more or less salubrious. If man pours into these streams and rivers the refuse of towns and cities, he must be prepared to meet the result of the experiment. It may be good—it may be bad to him: this he cannot know beforehand; but reason tells him that the experiment is likely to prove injurious. It may be less injurious than burying the excreta in cesspools under his house, or court, or garden;35 but this I doubt. In the meantime, how does civilized man protect himself from a source of disease respecting which there never was a doubt—the natural humidity of the soil on which he has erected his dwelling, in which he sleeps and lives? To meet this evil he forms surface drains around his house and garden and court. Into these collect the humidity natural to the soil, as well as rains of heaven. These drains, adulterated by no intermixture with the refuse of house and stables, terminate in the nearest streams, and serve to maintain these streams and rivers into which they flow at their natural standard.
Thus, before it was discovered that the best way of dealing with these difficult questions was to break down the distinction between drain and sewer (thus poisoning, probably for all time to come, the air of towns and cities), construct a sewer which soon becomes a cloaca to receive all, and in open day and above ground throw the contents into the nearest stream—imitating old Rome, without knowing anything of Rome’s municipal economy, our forefathers drew a marked and clear distinction—1st, between drain and sewer; 2nd, between a cesspool and a dead-well; 3rd, between the excreta of man, which they knew to be offensive, and that of animals, which all were well aware are innoxious: the latter they restored to the fields, the former they disposed of as best they could.
Society, having rejected in this instance the experience of their forefathers, enters now on a new phasis. Nature, about which they talk so much, will not suffer them to rest half way. Bad odours pervade the streets, courts, and houses: rivers can scarcely be approached. Chemists affirm that that which is thrown into the sea should be returned to the land. It is this question, in so far as it bears on the matter discussed in this chapter, I shall now briefly discuss.
There lie before me the “Letters on Chemistry” of an illustrious German chemist.36 They contain the expression of the latest scientific results hitherto attained. Whatever view those who follow us may adopt, we must in the meantime accept, to a certain extent, of those contained in these “Letters.” A phenomenon must be accepted as a fact until refuted by another; and the last experiment, until refuted, expresses the nearest approach to that truth which, up to the moment, man had been able to attain. Simple observation tells man many truths. It shows him that out of grass, herbivora, or grass-eating animals of all kinds—from the timid hare to the swift and powerful horse—from the fierce buffalo to the sagacious and irresistible elephant—find the means for forming muscle and bones, viscera and skin. Out of a similar food man himself, though no doubt omnivorous, can also derive the means of support. The rice-eating population of India are not deficient in energy; whilst it is equally certain, though less surprising, no doubt, that out of that which once was a living animal, man and the carnivora derive a considerable part of their subsistence.
No experiments can set aside these simple views, which indeed form the basis of all inquiry; but civilized man, as I have shown, appeals to the soil mainly for support. He trusts to the cerealia, and to those exuberant and abundant crops of legumina and of grains required for the support of herds of animals, which the uncultivated field could never maintain. Hence arose agriculture, the most useful of all the practical arts—not yet a science, but likely in time to become one.
Chemists assert—and I see no reason to doubt their experiments—that the ash of the blood of graminivorous animals is identical with that of the ash of grain; the incombustible constituents of the blood of men, and of such animals as consume a mixed food, are the constituents of the ashes of bread, flesh, and vegetables; the carnivorous animal contains in its blood the constituents of the ash of flesh.37 All these substances ought to be found in grass alone.
In these processes it would seem that phosphoric acid plays a most important, and, as it would seem, an essential part. To this I shall return: at present I merely consider man’s influence on the soil or earth he lives on, what he derives from it, and what he returns to it, and in what form it is and ought to be returned. If it be true that without trees there would be no underwood, no corn, and no crops,—for trees attract the fertilizing rain, and cause the springs perpetually to flow which diffuse prosperity and comfort,—then assuredly man ought to be most careful in interfering with nature. It is the remark, I think of the illustrious Humboldt, that when the white man took possession of certain districts of North America, vast forests prevailed everywhere. On taking possession, experience showed that agues prevailed, and that wheat might be grown successfully. The forests have been now destroyed, and agues have disappeared; but phthisis pulmonalis prevails, and wheat no longer grows to maturity. We interfere with the soil as nature made it when we force it to produce from one acre the natural produce of ten; we interfere with the processes of nature when we load the air with the products of thousands of furnaces, manufactories, and the poison exhaled from poisonous rivers and brooks; and we interfere with nature when we alter the constitution of those streams and rivers from a natural to an artificial state, loading them with the refuse of our artificially-drained fields, &c.
Let us listen to Liebig on a matter to which he has given the utmost possible attention:—
“Experience in agriculture shows that the production of vegetables on a given surface increases with the supply of certain matters, originally part of the soil which had been taken up from it by plants—the excreta of man and animals. These are nothing more than matters derived from vegetable food, which in the vital processes of animals, or after their death, assume again the form under which they originally existed as parts of the soil. Now we know that the atmosphere contains none of those substances, and therefore can replace none; and we know that their removal from a soil destroys its fertility, which may be restored and increased by a new supply. Is it possible, after so many decisive investigations into the origin of the elements of animals and vegetables, the use of the alkalies of lime and the phosphates, that any doubt can exist as to the principles upon which a rational agriculture depends? Can the art of agriculture be based upon anything but the restitution of a disturbed equilibrium? Can it be imagined that any country, however rich and fertile, with a flourishing commerce, which for centuries exports its produce in the shape of grain and cattle, will maintain its fertility if the same commerce does not restore, in some form of manure, those elements which have been removed from the soil, and which cannot be replaced by the atmosphere? Must not the same fate await every such country, which has actually befallen the once prolific soil of Virginia, now in many parts no longer able to grow its former staple productions—wheat and tobacco? In the large towns of England the produce both of English and foreign agriculture is largely consumed. Elements of the soil indispensable to plants, do not return to the fields; contrivances resulting from the manners and customs of the English people, and peculiar to them, render it difficult, perhaps impossible, to collect the enormous quantity of the phosphates which are daily, as solid and liquid excreta, carried into the rivers. These phosphates, although present in the soil in the smallest quantity, are its most important mineral constituents. It was observed that many English fields exhausted in that manner, immediately doubled their produce as if by a miracle when dressed with bone earth imported from the Continent. But if the export of bones from Germany is continued to the extent it has now reached, our soil must be gradually exhausted, and the extent of our loss may be estimated by considering that one pound of bones contains as much phosphoric acid as a hundredweight of grain.”
Many practical farmers, I am aware, still doubt the facts and theories of chemistry as applied to agriculture; with them I am free to admit that agriculture is not a science as yet, but an experimental art. With this I have nothing to do directly, my object being to show in this chapter in how far civilized man modifies and influences the soil on which he lives. He, the practical farmer, clings to farmyard manure, which he collects in heaps in his farmyard, or by the roadside, exposed to every change of weather, to drenching rains, to summer heat, and winter’s cold; from it run in streams over the roads the liquid parts of the manure, carrying with them the soluble salts; out of what is left when it has become rotten he hopes to restore to the field what it lost during the previous crop, and to a certain extent he succeeds; on the other hand, the chemist argues that the grand object of modern agriculture is to substitute for farmyard manure, that universal food of plants, their elements, obtained from other and cheaper sources retaining its full efficacy; and this can only be done when we shall have learned, what as yet we know but imperfectly, how to give to an artificial mixture of the individual ingredients the mechanical form and chemical qualities essential to their reception, and to their nutritive action on the plant; for without this form they cannot perfectly supply the place of farmyard manure. All our labours must be devoted to the attainment of this important object.
However this may be, and however it may be explained by the chemists, it must be admitted that to the accidental discovery of bone manure England owes many turnip crops, and to the introduction of guano from Peru and Ichaboe crops of wheat which no other manure as yet known could have produced. Peruvian guano, the best of all, is the excreta of a sea bird; these excreta, placed in a clear and perfectly dry atmosphere, have been exposed for centuries to a tropical sun; no rain falls on the heaps, trodden down only by the gentle feet of the birds themselves.
That out of such a product there should arise so excellent a manure surpasses all previous reasoning derived from mere science.38 It is obvious, then, that much still remains to be discovered. Were any proof of this required, we might refer to the agriculture of China, where, as has been reported, human excreta alone are used as manure, and with a success unequalled in any other part of the world. In that singular land they have discovered much, or using perhaps the discoveries of preceding races, have turned them to the best account. Their agriculture is said to be perfect.
With such a system of manure and such a population one might predicate a condition of earth, air, and water, incompatible with human life. Now the very reverse happens, at least, in so far as regards the Chinese themselves.
No land so teems with a population strong, active, and in robust health; true, it does not suit the European constitution; fever and dysentery sweep off the troops and sailors of European nations who visit the Celestial Empire for the purpose of trade or of plunder. There is a something unknown in the climate unsuitable to the European; the condition of the earth, air, and water of China, is fatal to him. In which of these does the noxious element reside—in all or in none? This is possible; but man in the meantime must decide by what he knows and see............