358 



On Nitrate of Soda. 



and so on the one hand relieving the farmer from expensive 

 delusions, on the other hand seeming genuine discoveries 

 against the mistrust of ignorance." In fact, these are not 

 merely the best, but the sole reliable, series of experiments upon 

 manures, and they have produced a great result in the discovery 

 of the only fundamental truth we possess in agricultural chemistry, 

 namely, that Nitrogen is the element mainly required as manure 

 on ordinary soils by our corn-crops.* Thus upon previously ex- 

 hausted land at Rothampstead, 3 cwt. of salts of ammonia, 

 applied for six successive years, raised the yield of Vv^heat at the 

 rate of nine bushels a-year, while 14 loads of dun^ raised it but by 

 eleven bushels, that is by only two bushels more. If the unassisted 

 nitrogen lagged somewhat behind the dung, thus proving that 

 the soil could not fully supply the mineral constituents of the 

 wheat-crop, this is quite immaterial for the purposes of common 

 farming, since in common farming white crops are alternated 

 with green ones — ammoniacal manures with phosphoric — and 

 even in the fifth year's repetition at Rothampstead, the amount 

 of yield marked no perceptible def ault of other ingredients, no 

 failure in the ammonia. 



This simple law explains the adoption of the multifarious 

 substances which practice had taught those v/ho went before us 

 to employ. Dung used everywhere, sprats applied in Thanet, 

 seaweed in the Lothians, rape-cake in Yorkshire, woollen rags 

 in Berkshire (not half cotton rags as they are now), soot, horn- 

 shavings — all these substances, however incongruous, and in 

 later times Guano, Gas-water, Nitrate, agree in nothing else, 

 but agree in this — that they contain Nitrogen, and, in as far as 

 they so agree, are capable of increasing our corn-crops. If any 

 one conversant with the theory of cultivation look back only ten 

 years, he will see how great an advance it is to have established 

 this principle, not as a conjecture only, but as an undeniable 

 law. As with most discoveries in other sciences, our eminent 

 chemists have all more or less anticipated the truth, but the owner- 

 ship must be appropriated to him who has proved it, and Mr. 

 Lawes has earned the high honour of establishing a principle of 

 the same importance in scientific Agriculture that gravitation 

 bears in Astronomy, or the circulation of the blood in Medicine. - 



The substance indeed which we are now considering was not 

 experimented upon at Rothampstead, and in some degree differs 

 from any that was used there, since nitrogenous substances 

 may be divided for our present object into three classes, — first, 

 those which contain ammonia (or urea convertible into ammonia), 



* Mr. Lawes by no means denies that mineral manures are sometimes useful, but 

 lie has proved that even then the ashes of the plant afford no safe indication of the 

 manure to be applied. 



