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Show 242 DISINTEGRATION CHAP. v. car b ona t eof .11·1ne and on the oxides of ir.o n. It is, also, known that some of t~ese acids, wh 1. c h were called loner"rl aeor o by The. nar. d. azo. - humw. , aro en..t bled to dissolve. collold Slhca. 11*1 t. to tlle nitroa-en wlnch theycontaln. pr~or 1on • b . In tho fornlation of these latter aClds worms pro nably afford solne aid, for Dr. H. Johnson 1. n f'o rm m e that by N ossler' s tes. t he .f ound O·O l8 per cent. of ammonia in t.hmr castmgs. The several humus-acids, whwh ~p~)e ~r, as we l mve J.U S t see rl , to be tO> 'ene•r ated • w1tlnn the bodies of wornls during the digestive process, and their acid salts, play a highly im~ortant. part, according to the recent ~usorvatwn~ of Mr. Julien, in the disintegration of vanous kinds .of rocks. It has long been known that the carbonjc acid, and no doubt nitrjc aml nitrous acjds, which are present in rain-water, act in like manner. There js, also, a ~rcat oxce s of carbonic acid in all soils, espccmlly in rich soils, and this js dissolved by the water * A , A , J Ul l.O ll "On the Geolocor ical acLion of.. .t he Ilnmus-aci3d1s1," 'nroc American Assoc. Science,' vol. xxvm., 1870, p. y ·J· .&: • • AI "Chemical erosion on Moun tam s ummt· t s ·' " 'New .0 1 ' so on . f S . s , Oct 14: 1878 as quoted in the 'Amencan Academy o • Clence ' · ' . ' u " llow Naturalist.' Ace also, on this subJect, S. W. Johnso ' Crops Feed," 1870, p. 138. CrrAP. V. AND DENUDATION. 243 in the ground. ':rhe living roots of plants, moreover, as Sachs and others have shown, quickly corrode and leave their impressions on polished slabs of marole, dolomite and phosphate of lirne. They will attack even basalt and sandstone.* But we are not here concern d with agencies which are wholly independent of the action of worms. The combination of any acid with a base is much facilitated Ly agitation, as fresh surfaces are thus continually brought into contact. This wilJ Le thoroughly effected with the particles of stone and earth in the intestines of wonns, during the ligestive process; and it shou1d Le ren1ernLered that the entire mass of tl1e mould over every field, passes, in the course of a few years, through their alimentary canals. Moreover as the old burrows slowly collapse, and as fi·esh castings are continually brought to the surface, the wl10le superficial layer of mould slowly revolves or circulates; and the fi·iction of the particles one with another will rub off the finest films of disintegrated matter as soon as * See, for references on thi::; subject, S. \V. Johnson, "How Crops Feed,'' 1870, p. 32G. R 2 |