THE FARMERS* REGISTER. 



713 



Tlius llio very cause wliicli in llie preceilitii^ 

 section WMs slioivii m oper.iu-. in consiaiiily diiiii- 

 iiishiniT ihii iiinuiinl oi aiiiniuiii,t in ilieair, wnJ 

 llie o|)t'r;iliuii ol' vviiitli cefMihly ri-njers iinproliii- 

 ble llie ('..xisleiice oi lliis coinpouiid in the alnio- 



oi nitralRs, to the jjresence of which iheir eflect 



on vei^claiion amy not uiilrcquenily be ascribed. 



To iliis /act we siiail liereader leciir. 

 Tlie soil?, in tlie plains of India, and in other 



similar &po;s in the Iropical regions, niav be re- 

 ephrre in ilie Kni^e (luaniity supposed by ecinie*— ■ garded as natural nilre-beds, in which the decay 

 this same canst; is at llie same moment consianiiy I ol organic n)alter being vasily more rapid Ihan in 

 reproducing niirio acul. And, though much ul | our temperate regions, liie produciion of nitric 

 wliat is thus produced must necessarily, at, in tlie j acid is rapid in [)roporiion.* 



case of ammonia, be carneti down to the sea by 4^- Eui in many localiiies in which the presence 

 the ratn-?, or be directly ahsorbed by the waters ol | ol organic mailer is not to be lecoirnized in sen- 

 the ocean themsflvee, yet il is otjvious that in sible quantity, ilie production of this acid is ob- 

 wliaitver proponion we may suppose the ammo- served to proceed wiih a constant and steady pace, 

 nia of liie air to reach the leaves and rools of Thus, fiom the walls of certain caves in Ceylon a 

 planis. in no less proponion must ihe niiric acid, | layer is yearly parfidoff, which yields an abundant 

 with which it is associaied, lie enabled to enter i ciop of saltpetre (Dr. John Davy). Tlie cele- 

 into the circulating sysiem of the various tribes brated Mammoth cave in Kentucky, situated in 

 of living vegetables, tliai rtourish on every quarter a limesione ridge, yields an inexhaustible supply of 



ol' the glutie 



3°. Again we have seen that, during the decay 

 of vegetatile substances in moist a;r, ammonia is 

 I'ornieii at the e-xpense of the hydrogen of the wa- 

 ter, and of the nitrogen of ineair. In lonsequence 

 of, or in connexion wiih siu h decay, niinc acid 

 is also largely protluced in nature. 



The most liiiuiliar, as well as the most instruc- 

 tive, exan)ples of tins ((jrmation tf nitric acid is 

 in iheartiticial nitric-feds ol France and the north 

 of Europe. 'I'hese are lurinetl by mixing eariii 

 ol' ditlerent kinds with stable manure or other ani- 

 a)al and vegetable matiers, and ex[)osing ihe 

 mixture to the air in long ridges or conical heaps, 

 which are occasionally watered wiili I, quid ma- 

 nure, and turned over lo expose fresh portions to 

 the air. Altera time, perha! s once a year, the 

 whole is washed, vviien the. water which comes 



nitrate of lirne. During the war with Great 

 Britain, fifty men were constantly employed in 

 lixiviating the earth of this cave, and in about 

 three years the washed earth is said to become as 

 strongly impregnated as at first. Through the 

 cave a strong current of'air is con'inually rushing, 

 inwards in winter and out wards during tlie summer 

 months. On the plaster of old walls, especially in 

 damp situations, an tffloiescence of this and other 

 nitrates is frequently observed over every part of 

 Europe, In China, according to Davis, the old 

 plaster of the honsps is so much esteemed as u 

 nicKiure, that pariies will often I'Uichase it at the 

 expense of a coating of new plaster. Old clay 

 walls, and especially the walls of clay-buili huts, 

 are said to be very lertilising to the land, when 

 applied as a lop-dressiiig ; and in --ome parts of 



England, where the land is poor, the people are 

 oil is Ibund to I'oniain a variable quaniiiy of the j said to pile up the soil in the form o( walls, in 

 nitrates of potash, soda, lime, and magnesia, order to improve its qu'iliiy. These latter /acts 

 which are employed (or the manulacture of salt- j seem lo indicate that both In China and in Eng- 

 petre. In tiiese niiric-beds it has been observed j land nitric acid is produced in similar circutn- 

 that the produciion ol' niliic acid either does not j stances, and that to iis production the fertilizing 

 take place at all, or only with extreme slowness, I action oftiie old plaster, and of'lhe weathered clay, 

 unless animal and vegetable matter he present in j ia alike to be atiribuled 



considerable proponion. And yet the quantity o 

 nitric acid which is Ibrmed is much greater than 

 could be produced l)y the oxidation ol' the wliole 

 of the nitrogen contained in the organic matters 

 piTseni. in the mixiure.t It is also observed that 

 the nitre-beds are more productive when a poriion 

 from one outer lace of the heap is lixivia'eJ Irom 

 time to lime, and the washed earlh added to the 

 oilier side, than when the wliole is lixiviated at 

 once, and again Ibrmed int.* a heap and exposed 

 lo the air. 



it a|)pears, therefore, that organic mailers are in 

 our ciimaie necessary to cause the lorraaiiori ol 

 nitric acid lo comrnence, but that after it has hegun 

 il will proceed in ihe same heap lor an indefinite 

 period, and ai the expense apparently ol the nitro- 

 gen (if the air only. 



Compost heaps are in general only artificial 

 nitre-beds — often unskilfully prepar( d ami badly 

 managed — producing, however, a certain quantity 



* £J^'e especially Liebig's Organic Chemistry ap- 

 plied lo J^iiciilture, p. 74. 



t Diiijiiis, Traiie de Ckemie, ii., p. 725. He adds, 

 that 100 lbs. of niiro coiitjir. the nitrogen of 75 lbs. of 

 ordinary aiiimai matter, siipposetl in a dry sta'e, or of 

 300 or -100 lbs. in its ordinary slate of irjoisture, — a 

 much greater relative proportion of animal matter 

 than is ever added to the heap. 

 Vol. IX.— 73 



In the cultivated soil, also, this acid is formed in 

 ordinary circumstances. Braconnot found liitrate 

 of potash in the botanic garden at" Nancy, in a 

 poriion of soii in which poppies (papaver soninifc- 

 runi) had grown luxuriantly for ten years in suc- 

 cession — in larger quantity in the soil surrounding 

 the interlaced roots of an esclepias incarnala, 

 growing itj an ordinary flovver-poi, wiih a fioie in 

 the boitom — as well as in moss-earth, in which a 

 l»lani ol' euphobia 6reo»i had been grown in a pni.t 



There is liiile reason to doubt, indeed, that 

 nitrates are to be Ibund, in greater or less quantity, 

 in all cultivated soils. 



I sliall not enter into a detailed inquiry how this 

 niiric acid is formed. It is probable ihat as in 



* We are as yet too little acquainted with the 

 natural history of the district of Arica in South 

 America, in which, as already stated, the nitrate of 

 soda has been accuiniilate.d in such large quantity, 

 to be able to say to what special cause tlie accumu- 

 lati(Ki is due. But as, from the description of Mr. 

 Darwin, the locality appears to liave been the site of 

 an ancient lake, it is not unlikely that the nilrate 

 may have heen derived from Ihe successive washings 

 of a«oil similar to that of India, by rains or periodi- 

 cal floods which lor a long period emptied them- 

 selves into or fed the lake. 



+ Jn. de Chim. et de Pkys., Ixxii., pp. 33 to 35. 



