344 Circulation of matter in the Aniinal ^* Vegetable Kingdojns. Vol. X. 



which one, namely, the soil, contains those 

 essential elements which are absent from 

 the medium surrounding them, that is, the 

 atmosphere. 



Is it possible that we could ever be in 

 doubt respecting tlie office which the soil 

 and its component parts subserve in the ex- 

 istence and growth of vegetables? — that 

 there should have been a time when the 

 mineral elements of plants were not regard- 

 ed as absolutely essential to their vitality? 

 Has not the same circulation been observed 

 on the surface of the earth, which we have 

 just contemplated in the ocean, — the same 

 incessant change, disturbance, and restitu- 

 tion of equilibrium? 



Experience in agriculture shows that the 

 production of vegetables on a given surface 

 increases with the supply of certain matters, 

 originally parts of the soil which had been 

 taken up from it by plants — the excrements 

 of man and animals. These are nothing 

 more than matters derived from vegetable 

 food, which, in the vital processes of ani- 

 mals, 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 these sub- 

 stances, 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 in- 

 vestigations into the origin of the elements 

 of animals and vegetables, the use of the 

 alkalies, of lime and the phosphates, any 

 doubt can exist as to the principles upon 

 which a rational agriculture depends? Can 

 the art of agriculture be based upon any 

 thing but the restitution of a disturbed equi- 

 librium? Can it be imagined that any coun- 

 try, however rich and fertile, with a flourish- 

 ing commerce, which for centuries exports 

 its produce in the shape of grain and cattle, 

 will maintain its fertility, if the same com- 

 merce does not restore, in some form of ma- 

 nure, those elements which have been re- 

 moved from the soil, and whicli 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 pro- 

 duce both of English and foreign agricul- 

 ture is largely consumed; elements of the! 

 soil indispensable to plants do not return tO; 

 the fields — contrivances resulting from the 

 manners and customs of English people, andj 

 peculiar to them, render it difficult, perhaps^ 



impossible, to collect the enormous quantity 

 of the phosphates, which are daily, as solid 

 and liquid excrements, carried into the rivers. 

 These phosphates, although present in the 

 soil in the smallest quantity, are its most 

 important mineral constituents. It was ob- 

 served 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 hitherto reach- 

 ed, 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 hundred weight 

 of grain. 



The imperfect knowledge of nature, and 

 the properties and relations of matter, pos- 

 sessed by the alchemists, gave rise, in their 

 time, to an opinion that metals as well as 

 plants, could be produced from a need. The 

 regular forms and ramifications seen in crys- 

 tals, they imagined to be the leaves and 

 branches of metal plants ; and as they saw 

 the seed of plants grow, producing root, 

 stem, and leaves, and again blossoms, fruits 

 and seeds, apparently without receiving any 

 supply of appropriate material, they deemed 

 lit worthy of zealous inquiry to discover the 

 \seed of gold, and the earth necessary for its 

 jdevelopment. If the metal-seeds were once 

 jobtained, might they not entertain hopes of 

 their growth ? Such ideas could only be 

 entertained when nothing was known of the 

 atmosphere, and its participation with the 

 earth, in administering to the vital processes 

 of plants and animals. Modern chemistry 

 indeed produces the elements of water, and, 

 combining them, forms water anew; but it 

 does not create those elements — it derives 

 them from water; the new-formed artificial 

 water has been water before. 



Many of our farmers are like the alche- 

 mists of old, — they are searching for the 

 miraculous seed — the means which, without 

 any further supply of nourisimient to a soil 

 scarcely rich enough to be sprinkled with 

 indigenous plants, shall produce crops of 

 grain a hundredfold. 



The experience of centuries, nay, of thou- 

 sands of years, is insufficient to guard men 

 against these fallacies; our only security 

 from these and similar absurdities must be 

 derived from a correct knowledge of scien- 

 tific principles. 



In the first period of natural philosophy, 

 organic life was supposed to be derived from 

 wator onl}'; afterward, it was admitted that 

 certain elements derived from the air, must 

 be superadded to the water; but we now 



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