318 ' IS NITRIC ACID FOOD FOR PLANTS ? 



the earth ; and we may expect the production of the latter 

 wherever ammonia, and the conditions for its oxidation, are 

 found united. 



The occurrence of large beds of nitrates in America cannot 

 afford the most distant reason for the assumption that they are 

 formed in an unusual way ; it is unnecessary to call in the as- 

 sistance of the nitrogen of the air, in order to explain their great 

 extent. We find in nature whole mountains consisting of shell- 

 fish, and of remains of microscopical animals, which must have 

 contained a certain quantity of nitrogen when alive. We find 

 also large layers of animal excrements (Coprolites), which place 

 beyond all doubt the former existence of innumerable individuals 

 of species now extinct. In the processes of decay and putrefac- 

 tion to which they have been subjected, the nitrogen of their 

 bodies could have escaped only in two forms ; in cold climates, 

 it would assume the form of ammonia, and in warmer countries, 

 the form of nitric acid, which must accumulate wherever the 

 salts formed by means of it are not carried off by water. 



Ammonia, however, is not the only source of the formation of 

 nitric acid. In the action exerted by the electric spark on the 

 constituents of air (which are also the constituents of nitric acid), 

 we recognise a second source, which, to all appearance, is very 

 extended. 



Cavendish was the first to observe, that by a continued passage 

 of electric sparks through moist air, its volume diminished, and 

 an acid, soluble in water, was formed at the same time. This 

 great philosopher proved, by a series of decisive experiments, 

 that the constituents of the air, the nitrogen and oxygen, united 

 to form nitric acid when exposed to the influence of electricity. 



Now it is probaule 'that lightning (the most powerful electric 

 spark known), in its passage through moist air, may effect a com- 

 bination of the constituents of air, in consequence of which nitric 

 acid would be formed. 



In an examination of rain-water, which the author of the 

 present work undertook in the years 1826-1827 (Annales de 

 Chimie et de Physique, xxxv., 329), it was actually found that 

 out of seventy-seven analyses made of the residue of rain-water, 

 seventeen of them, obtained by the evaporation of the rain of 



