ELISHA MITCHELL SCIENTIFIC SOCIETY. 



113 



where the content of carbonate of lime is exceptionally high, 

 still with such soils as those containing only a fraction of a per 

 cent, it is not likely that the action is nearly as great, unless it 

 is due to other causes. 



The precipitation does not take place till the acid phosphate 

 is dissolved l>y the rain or soil moisture, and so conies in more 

 intimate contact with the various soil particles. This explains 

 the fact that the action of superphosphates is more apt to be 

 feeble in dry weather than at any other time. In some instances 

 particles of acid phosphate, after having been in the soil for six- 

 weeks of continuous dry weather, have been examined and have 

 been found acid and unchanged. 



The following experiments are cited to illustrate the action of 

 various soils on superphosphates. The original calculations are 

 further extended so as to be more comparable one with the other: 



I. Voelcker, in I860,* showed that every soil, without excep- 

 tion, acts at once on the superphosphate as soon as it comes in 

 contact with the moist surface. He experimented with various 

 descriptions of soils, using in each case, however, a very large 

 excess of water. To 12 oz. soil were added 109.24 grains or 

 nearly J oz. of superphosphate (containing 40.6 grains soluble 

 phosphate) dissolved in 1J pints of water; or to 12 oz. of soil 

 nearly J oz. soluble phosphate was used; equivalent to 1 part 

 of soluble phosphate to 100 parts of soil. With these amounts 

 he obtained the following results (Table 1): 



TABLE I. 



SHOWING ACTION OF SOILS OX srPERPHOSPHATES-VOELCKER'S RESULTS. 



*Cited by H. von Liel.ig, Roy. Ag. Soc, 19, 1, p. 283. 



