220 TALKS ON MAN CUES. 



These explanations arc no donltt pood as far as they iro, but 

 experience furnishes many fads wliieh cannot beexphiiiied by any 

 one, or all, of these suppositions. Lime, we all know, does much 

 good on soils abounding in orjranij matter, and so it frequently 

 does on soils ahnost destitute of 't. It may liberate pi)tasii, soda, 

 silica, •■tc, from clay soils, i)ut the application of potash, soda, and 

 silica has little benelicial effect on the soil, and therefore we can- 

 not account for the action of lime on the supposition that it ren- 

 ders the potash, soda, ct<'.,of the soil available to plants. Further- 

 more, lime ctFecls great siood on soils abounding in salts of lime, 

 and thcref'-re it cannot be that it operates as a source of lime for 

 the structure of the plant. 



None of the existing theories, therefore, aatisfr.ctorily account 

 for the action of lime. Prof. Way's views are most consistent with 

 tljc facts of practical experience; but they are confes.sedly hypo- 

 thetical ; and his more recent investigati(ms d'» not confirm the 

 idea that lime acts beneficially by converting the soda silicate into 

 the lime silicate. 



Thus, six .<;oils were treated with lime water until they had alv 

 sorbed from one and a half t » two per cent of their weight of limo. 

 This, supposing the soil to be six inches deep, would be at the rate 

 of about 300 bushels of lime p r acre. Tiie amoimt of ammonia in 

 the soil was determined before liming, after liming and then after 

 being exposed to the fume-i of carltonale ammonia until it had ab- 

 sorbed as much as it would. The following table exhibits the results: 



iNo. 1.1 No. a. No. 8. No. 4. No. 5. No. 6. 



Ammonia in 1,000 prains of natural I 



soil O.Sai'o.lSl 0.08.". 0.109 0.137 O.0S3 



Ammonia in l.()00 gniius of Boil af.er I i 



limin;^ 0.1(» 0.102 0.040 O.OSO 0.051 



Ammonia in 1.000 ;;ni!na of soil after III 



limin:; and cxpoBiirc to the vopor of 'I 



ammonia 2.226 ! 2.060 .'$.297 1.070 3.265 1.887 



Ammonia in 1.0 tO grain;' of soil after i 



exposure to am monia without liming 1.506 2.557 .3.286 1.097 2.615 2 .088 



No. 1. Surface .«i)il of Lo-idon clay. 



No. 2. Same soil from I^ ti> 2 feot below the eurface. 



No. :i. Same soil ."J f'-ot hi low tho surface. 



No. 4. Loam of tertian- drift I feet below the enrfacc. 



No. .I. (Jau't clay— surfaci,' soil. 



No. 6. Ciraltclay 1 feet below the surface. 



It is evident that lime neither assisted nor interfered with the 

 absorption of ammonia, and hence the beneficial effect of liming 

 on such soils must be accounted for on some other supposition. 

 This negative result, however, does not disprove the truth of Prof. 

 Way's hypothesis, for it may be that the silicate salt in the natural 

 soils was that of lime and not that of soda. Indeed, the extent to 



