Af/ricultural Chemistry. 289 



added to the land in the forms of manure from cattle, corn, and 

 guano (I assume annually 100,000 tons of guano, with an average 

 of 4'5 per cent, of nitrogen), does not make up one-third part of 

 this loss ; and that the loss increases annually with the increase 

 of population. Previous to 1840 our supposed observer would 

 have seen, to his amazement, that Great Britain only received, to 

 make up for the constant loss of nitrogen, a still smaller fraction 

 of the lost nitrogen, and that, in spite of this, the fertility and 

 productiveness of the English soil not only was not diminished, 

 but has uniformly increased for centuries past ; nay, that the 

 supply of nitrogenised manure in the dung-heaps of English 

 farmers has been augmented. 



All the nitrogen of plants and of animals is derived from the 

 air. Every fireplace where coals are burned, the numerous fur- 

 naces and chimneys of the manufacturing towns and districts, of 

 locomotive engines and steam-ships, all the smelting furnaces of 

 the iron-works — all these are so many forms of distillatory appa- 

 ratus which enrich the atmosphere with the nitrogenised food of 

 a vegetable world belonging to a period long past. We can form 

 some idea of the quantities of ammonia thus poured into the atmos- 

 phere if we consider that in numerous gas-works many tons of 

 ammoniacal salts are annually obtained from the coals distilled 

 for gas. 



In other words, if all the nitrogen or all the ammonia which 

 Great Britain sends into the sea and the air from her towns and 

 fields, and which is thus lost to her, had been exported, not as 

 ammonia, but in the forms of cattle and corn, in her sliips, for 

 centuries past, she would not be poorer in nitrogen by a single 

 pound than she now is. No doubt she might have been richer 

 in nitrogen had this loss not taken place ; but she could not 

 have been poorer than she now is, because, in consequence of the 

 cultivation of her soil, the nitrogen lost by the land in the forms 

 of cattle and corn is restored to it by the atmosphere, which is 

 everywhere, and conveys its benefits to every spot — which leaves 

 the place where it has yielded nitrogen to the soil for another 

 where it is again supplied with that substance. 



But if the soil of a country cannot lose its fertility by the loss 

 of ammonia, the question remains, whether its fertility can be 

 increased by the addition oi ammonia alone? that is, whether the 

 soil by this means can acquire the power of producing, in a 

 series of years, say in fifty years, more corn and more cattle than 

 it would have produced in the same period without this addition ? 



The answer to this question is obvious, if we inquire on ickat 

 the fertiliti/ of our soil, on ivhat its augmented produce, and on 

 what the continuance of this augmentation of produce depend. But 

 before I enter more minutely uito these (questions, I must beg 



VOL. XV IL U 



