50 



Essay on the Analysis of Soils. 



A pooer soil, of which the component parts were 



Sihcious Sand . . . 64.0 



Clay 32.3 



Calcareous Sand ... 1.2 



Carbonate of Lime . . 1.2 



Humus 1.3 



had a specific gravity of 2.526. 



These examples suffice to show that the specific gravity of a 

 soil is some tolerable indication of its fertility. It cannot, how- 

 ever, be entirely relied upon in the absence of other proofs ; for 

 there may be many different mixtures of earths which will have the 

 same specific gravity, although they may differ greatly in their 

 fertility ; but it will facilitate the analysis, and often detect mis- 

 takes in the process, if the result does not accord with the specific 

 gravity found. 



We proceed now to the analysis. The portion of soil which has 

 been deprived of all its water, as described above, must be sifted 

 through metallic sieves of different fineness ; the first is made of a 

 perforated tin plate, the holes of which are about one-twentieth of 

 an inch in diameter. Whatever does not go through this is put 

 by. The remainder is successively passed through two or three 

 more sieves, increasing in fineness to the last, which is of the finest 

 wire-cloth, having from 1 50 to ] 70 threads in an inch : whatever 

 passes through this is an impalpable powder. 

 Thus we have already a division of the soil ac- 

 cording to the size of its particles : — 1st, the 

 coarse grit left in the first sieve ; 2nd, the finer 

 grit in No. 2 ; 3rd, fine sand in No. 3 ; and 4th, 

 impalpable powder, which has passed through 

 the last sieve. To facilitate this part of the ope- 

 ration the sieves may be made so as to fit into 

 one another, like the filterers in a coffee-biggin, 

 the last fitting into a tin pot which will hold about 

 a pint of water ; a cover being made to fit on the 

 top sieve, the instrument is complete. (See Fig.) 

 Thus all the sifting may be done at once, without 

 any loss. Any lumps which are not thoroughly 

 pulverized must be broken. The coarser sand 

 left in the sieve No. 1 must now be washed with pure water to de- 

 tach any fine dust adhering to it ; what runs through may be used 

 to wash No. 2, in the same manner, and then may pass through 

 No. 3 to the impalpable matter which passed through all the 

 sieves. A sufficient quantity of water must be used to render the 

 whole of this last nearly fluid. There will then be three different 

 portions of the washed soil left in the sieves, and a portion of im- 

 palpable matter diffused through the water in the lower division 



