264 LIME INDUCING TIIE FORMING OP NITRATES. 



to judge of many of the chemical doctrines and facts presented by 

 Johnston; but infer that they are among the unquestioned results 

 of the latest and ablest chemical researches. As a matter of course, 

 the scientific author may be supposed to have no personal acquaint- 

 ance with practical farming. But his numerous agricultural facts, 

 though received from other persons, are not less the fruits of 

 practice and observation, and therefore are worthy of much respect, 

 even when not to be admitted as conclusive. Though knowing 

 nothing of this author, except from his book, and confessedly unfit 

 to decide on the correctness of many of its scientific positions, 

 still I accept this work as the latest and fullest embodiment and 

 digest of the now received doctrines of agricultural chemistry in 

 Europe, and of agriculture in England ; and so esteeming the work, 

 it will be again referred to, as has been done before, whether for 

 support of my own positions, as in many previous citations or to 

 derive new lights and information, as now, or to oppose or refute, 

 as has been attempted in other cases. 



This section will present additional effects and valuable opera- 

 tions of calcareous manures, for which subjects, either wholly or 

 in part, I am indebted to Johnston, and to whom the credit"" due 

 will be particularly as well as thus generally awarded. The most 

 interesting and important of such new or additional positions, is 

 the power of calcareous earth, in soil, or in compost heaps of 

 manure, to form nitrates from atmospheric supply of material. 



The same two elements, oxygen and nitrogen, which when in- 

 termixed in gaseous form, and in certain uniform proportions, serve 

 to make atmospheric air, will, when chemically combined, consti- 

 tute nitric acid. Such combination is produced by electricity. f< It 

 is known," says Boussingault, " that so often as a succession of 

 electrical sparks passes through moist air, there is formation and 

 combination of nitric acid and ammonia. Now nitrate of ammonia 

 is one of the constant ingredients in the rain of thunder-storms." 

 (p. 494.) " The currents of electricity which in nature traverse 

 the atmosphere must produce the same effect [of forming nitric 

 acid], and the passage of each flash of lightning through the air 

 must be attended by the formation of some portion of this acid." 

 (Johnston, p. 160.) 



Ammonia, the volatile or aeriform alkali, is a chemical compound 

 of nitrogen (azote), one of the two elements of atmospheric air, 

 and hydrogen, one of the two elements of water. JbJence, of am- 

 monia, as of nitric acid, there are in the ordinal y moi.4 air of the 

 atmosphere, the most abundant materials for both ihesc compound, 

 products. There is wanting only the agency for their formation, 

 which is exercised by nature only (as by lightning), and Uvit spa- 

 ringly, though incessantly, in some or other regions of the tnio- 

 gphere. Both ammonia and the nitrates (the certain and jj 



