Nitrate of Soda as a Manure. 



379 



genous matters : but whether they act upon plants in two forms, 

 Ammonia and Nitric acid, or whether by some secret of nature 

 either of these forms is transmuted into the other before it serves 

 the purpose of vegetable nutrition, is a question reserved for the 

 future decision of agricultural chemists.* 



Singularly indeed, while we are discussing the question, it 

 has been discovered at Paris that nature supplies to plants both 

 forms of nourishment indifferently in every shower. Our Eng- 

 lish chemist Cavendish showed in 1781 that the electric flash 

 might produce Nitric acid in the atmosphere. Liebig has since 

 ascertained the actual existence therein of Ammonia. Monsieur 

 Barral, having examined the rain-water collected at Paris last 

 year and the year before, has found in every shower an amount 

 of each substance, reaching in the course of a year the following 

 quantities severally per English acre : f — 



Nitrogen. 



lbs. lbs. 

 Ammonia . . . . 12-29 = 10 69 

 Nitric acid . . . . 41-24 = 10-12 



Still this large amount of manuring substance might be derived 

 by the atmosphere of Paris from the smoke and the foetid exha- 

 lations which float above every great capital, and much doubt was 

 accordingly felt by continental chemists on the whole result of 

 the investigation. It seemed desirable, therefore, to repeat the 

 experiment in pure country air. Accordingly rain-water was 

 collected by me last October at this place, which is remote 

 from any large town, except Oxford, from which the wind did 

 not blow while the showers took place. It was analysed by 

 Professor Way ; and, supposing our annual fall of rain to be 28 

 inches, the amount of manure yearly poured down from the 

 clouds on our soil would be larger than even at Paris. For it 

 would stand thus : — 



Guano 

 Nitrate of without 

 Nitrogen. Soda. Phosphates. 



lbs. lbs. lbs. lbs. 



Ammonia . . . . 28-59 = 23-54 = 159^^ = 164 

 JNitric acid . . . 68-91 = 17-88 = 121 = 124/^ 



Annual downfall of manure per acre 41-42 = 280^^ = 288/^j 

 It appears that in a year of ordinary rain the skies give us 



For a very instructive inquiry into the difficult subject of nitrification, see 

 Experiences Chimiques et Agronomiques, par F. Kiihlman. Paris, 1847.' This 

 ■work also contains a series of experiments proving the nitrogenous hypothesis of 

 manures ; and also a direct experiment establishing the action of nitrate of lime, 

 ^hich had not previously come to my knowledge. 



t The figures of M. Barral are so corrected by Dr. Wilson. 



