NITRIC ACID EXISTS LI RGELY IN NATURE. 159 



o[ that which is constantly undergoing decomposition by the agency ol 

 causes such as tliose above described. 



lint is the indefinite quantity of ammonia reproduced by these indi 

 rect melliods sufficient to replace all that is lost? Can it be supposed 

 to im])art to plants all the nitrogen they require ? These questions will 

 be considered in the following section. 



§ 5. Of the supply of nitric acid to plants.' 

 In regard to the action of nitric acid upon vegetation it is known — 

 1°. That when, in the form of nitrates of soda, potash, (tec, it is 

 spread upon the soil, it greatly promotes the growth and luxuriance of 

 the crop and increases its produce ; and 



2°. That, when other circumstancs are favourable to vegetation — as 

 in certain districts in India — the presence of an apj)reciable quantity of 

 these nitrates adds largely to the fertility of the soil.* 



The same effects are uncpiesiionably produced by the addition of am- 

 monia or by its natural presence in the soil. The beneficial influenco 

 of both compounds, then, behig recognized, the relative extent to which 

 each operates u\)on the general vegetation of the globe will be main 

 ly determined by the circumstances and the quantity in which they res 

 pectively exist or are reproduced. 



In regard to the existence of nitric acid, it is not known to form a 

 necessary constituent of any of the solid rocks of which the crust of the 

 globe is composed, but is diffused almost universally through the soil 

 which oversi)reads the surface. In the hotter regions of the earth, in 

 India, in Africa, and in South America (p. 56), it in many places accu- 

 mulates in sufficient (luantity to form incrustations of considerable thick- 

 ness over very large areas, and in many more it can be separated bj 

 washing the soil. liven in the climates of Northern Europe, it is rare- 

 ly absent from the water of artificial wells, into which the rains, aftei 

 filtering through the surface, are permitted to make their way.f 



On the whole, nitric acid and its compounds apj)ear to exist, ready 

 formed in nature, in larger quantity than either ammonia or any of its 

 compounds. 



* For the following, and other interesting notices, regarding Indian agriculture, I am in- 

 debted to Mr Fleming, of IJarochan, in Renfrewshire, whose long residence in the districts 

 to which he alludes, as well as the interest he takes in practical agriculture, renders his tes- 

 timony very valuable : 



"The districts of Ciiaprah, Tirlmot, and Shahabad, near Patna, where a large proportion 

 of the saltpetre sent fri>m Bengal is producei. are considered the most fertile in Bengal, 

 producing 2 and sometimes 3 crops yearly. The natives of these districts, particularly a 

 caste caJledQuirees (hereditary gardeners), Vv?)o cultivate the best land, and produce the 

 best crops, are in the liabit of irrigating their fields with water from wells so strongly im- 

 pregnated witli saltpetre and other salts as to he quite brackish, and they consider onions, 

 turnips, and peas, most benefitted by this irrigation. Grain crops also grow most luxuriant- 

 ly on lands yielding saltpetre, where there is enough of rain within a week or two after the 

 seed is sown, but if a drought follow.s the sowing, and continues for 3 weeks or a month, the 

 leaf becomes yellow, and the crop fails. 



"The Iliudoos do not generally manure their lands, as the dung of the cattle is used for 

 fuel, but the Quirees collect the ashes of cow dung and of burned" wood, and use it as a ma- 

 nure in some cases, chiefly for the poppy plant. 



"The Hindoos have for ages been well acquainted with (he rotation of crops, and. the ad- 

 vantages of fallowing land, although a great proportion of the land is almost consfautly in 

 rice, Indian corn, or millet, during the rainy season, and in wheat or peas during the' dry 

 season," 



t It occurs in the wells of the neighbourhood of Berlin (Mi(schorlich), in the form of ni- 

 trates of potash, lime, and magnesia, in the wells around Stockholm, and may be expected 

 in all wells that are dug (Berze lius).— 2Vai7c de Chrmie, iv., p. 71. 



