Guano as compared with Manure. 341 



of their particles. I therefore procured a sieve of the finest 

 gauze, the largest meshes of which by accurate measurement 

 did not exceed one-sixtieth of an inch in diameter. The 

 soil was then broken in a porcelain mortar, care being taken 

 that only the dried particles were crushed, without triturat- 

 ing any of the silicates or earthy matter. One hundred parts 

 of six samples so treated, Avere sifted upon the sieve before 

 described, and left the following small quantities of coarse 

 residue ; of this residue, it should be stated, that it was com- 

 posed in part of vegetable fibres and undecomposed organic 

 matter. Of soil No. 1, seven parts in one hundred remained 

 upon the sieve ; of No. 2, one and six-tenths parts ; of No. 3, 

 a subsoil, from twenty to thirty parts ; of No. 4, six and three 

 tenths ; of No. 5, one and five tenths ; of No. 6, eight parts 

 in one hundred. 



This remarkable comminution of the particles of these 

 soils, gives us at once a clue to the secret of their great fer- 

 tility. With this fineness an increased power is given to a 

 soil for the absorption, retention and condensation of moist- 

 ure, carbonic acid, and ammonia, an opportunity for the free 

 permeation of atmospheric air, a facility to the rootlets of 

 plants for extension, and a consequently increased facility for 

 receiving and appropriating nourishment. Indeed, a soil but 

 scantily provided with the inorganic constituents deemed 

 necessary for the support of vegetable life, but gifted with 

 this fineness of the elementary particles, must possess great 

 elements of fertility. I consider the existence of a large pro- 

 portion of finely divided matter in a soil, of almost as much 

 consequence so far as regards its fertility, as its chemical con- 

 stitution is. It must be also evident, that a soil composed in 

 great part of siliceous matter (as many of the fertile western 

 soils are), may, if the particles possess sufficient fineness, as- 

 sume to a considerable extent the good properties and charac- 

 teristics of an aluminous soil, without its bad ones. As an 

 illustration of this I would state, that one of the best tobacco 

 soils upon the Island of Cuba, some time since examined by 

 Dr. A. A. Hayes of Boston, was found to contain ninety per 

 cent, of the peroxyd of iron. And yet this soil, which we 



