SOIL. 



substances of which it is composed. 

 In the examination and analysis of 

 soils for the purpose of ascertaining 

 their power of production, we must, 

 therefore, fust examine them mechan- 

 ically, and afterward chemically, and 

 on this principle has been proposed 

 the mode of analy-ing soils, in a pa- 

 per which obtained one of the first 

 prizes given by the Royal English 

 Agricultural Society, and published 

 in the first number of its journal. 

 We will here insert a short account 

 of the process, with such alterations 

 and additions as more extensive prac- 

 tice has suggested. 



" There are two easy methods of 

 ascertaining the size of the particles of 

 a soil. The first and simplest is by 

 drying the portion under examination, 

 gently triturating it with a wooden 

 pestle in a mortar, so as not to pro- 

 duce a grinding of the more solid 

 portions, and then separating the 

 coarser from the finer parts by means 

 of several metallic sieves of different 

 fineness. A simple instrument is rec- 

 ommended for this pur- 

 pose, which is very porta- 

 ble, and consists of three 

 or four sieves fitting into 

 each other ; the coarsest 

 sieve being uppermost and 

 J covered with a lid ; the fi- 

 nest fitting into a recipient, 

 and the whole forming a 

 cylinder three or four inch- 

 es in diameter, and from 

 six to eight in height. The 

 coarsest sieve has threads 

 at the distance of -^^ of an inch, the 

 second has 80 in an inch, the third 

 120, and the fourth is the finest me- 

 tallic tissue which can be made. 

 What remains in the first two is ea- 

 sily examined by the eye, or with the 

 help of a lens. The third and fourth 

 require a microscope to see whether 

 any crystallized particles remain in 

 the impalpable dust which has gone 

 through all the sieves. By carefully 

 weighing these different earths their 

 proportion is known, and by taking 

 the specific gravity of each their na- 

 ture can be guessed at with tolerable 

 accuracy. 

 732 



" As this analysis is not intended 

 for experienced chemists, the sim- 

 plest methods are preferred to the 

 more accurate. There is a mode of 

 taking the specific gravities of sub- 

 stances which are in the form of pow- 

 der insoluble in water, so easy and 

 so little liable to error, that any per- 

 son, however unaccustomed to exper- 

 iments, can soon become sufficiently 

 expert to have full confidence in the 

 result. It is as follows : a small, 

 pear-shaped vial is blown of thin 

 glass, and the neck cut and ground 



smooth. The size is such as to con- 

 tain 300 grains of water, more or 

 less ; the exact quantity is not essen- 

 tiah It is now filled with pure water 

 at 60° of Fahrenheit's scale, and ac- 

 curately poised in a delicate balance : 

 100 grains weight are then placed in 

 the same scale with this vial, and, 

 by means of a very fine tube, water 

 is gradually sucked out of the vial 

 till the equilibrium is restored ; that 

 is, exactly one hundred grains of wa- 

 ter have been taken out. A counter- 

 poise is now made of lead or brass, 

 when the 100 grains weight has been 

 removed, and this serves for all fu- 

 ture experiments. When the specif- 

 ic gravity of any substance is requi- 

 red, the vial, partly filled with wa- 

 ter, is placed in one scale, and the 

 counterpoise, made as above descri- 

 bed, is placed in the other ; water is 

 added or taken from the vial till an 

 equilibrium is obtained. The sub- 

 stance to be tried is slowly and care- 

 fully poured into the vial, until the 

 water rises to the ground surface of 

 the neck and stands quite level, which 

 is easily seen by observing the reflec- 

 tion of the light from the surface. It 

 is then carefully replaced in the scale, 

 and grain weights are added to the 

 other scale to restore the equilibrium. 



