REPOET OF THE CHEMIST. 161 



' Whilst these differences are enormous, still the methods are hardly 

 comparable. That of Schloesing's has for its object the separation of 

 the clay in almost a pure state from the sand, lime, and other materials 

 which accompany it. Masure's and Noeble's apparatus make use of the 

 mechanical action of a stream of water to separate the soil into more or 

 less line particles. 



OBJECTION TO THE MECHANICAL ANALYSIS OF A SOIL. 



The objection most frequently urged against such mechanical analy- 

 sis is, that the lightest portion, most commonly called clay, contains, 

 in addition to that body, some very fine sand, some calcareous or feld- 

 spathic products, in addition to organic matter in a fine state of division. 

 This cause of error has long been pointed out by Boussingault, Gasparin, 

 and other authors. 



PRINCIPLE APPLIED TO MOST OF THE APPARATUS USED FOR THIS 



PURPOSE. 



The principle adopted in most apparatus used for this purpose is the 

 mechanical action of a stream of water flowing through the soil into a 

 succession of vessels, each somewhat larger than the one preceding, and 

 in which a certain amount of sediment is gradually deposited, beginning 

 with the coarsest and heaviest particles and ending with the very finest. 

 A weighed quantity of the air- dried soil is taken, and the action of the 

 water continued until it runs through the last vessel used perfectly 

 clear ; the different deposits are collected, dried, ignited, and weighed 

 separately. The results obtained are only approximate, and differ in the 

 same soil using the same apparatus. 



A succession of metal sieves, ranging from ten to one hundred meshes 

 to the square inch, are sometimes used for this purpose, a weighed quan 

 tity of soil being taken and the portion remaining on each sieve being 

 collected and weighed. 



THE EFFECT OF VARIOUS PROPORTIONS OF SAND IN THE SOIL. 



According to Thaer (Peligot, p. 158), when the sand and clay are of 

 equal parts, or in the proportion of 40 of sand to 60 of clay, comprising 

 under this name the finest sand, &c., as found in mechanical analysis, 

 the soil is fitted for all kinds of crops ; with more than 60 per cent, of 

 sand they are suitable to rye and barley, rarely for wheat ; with 70 per 

 cent, of sand the soil is suitable still for the cultivation of barley, and 

 especially for the cultivation of rye ; it is easily worked, but manures 

 are raijidly used up. With 90 per cent, of sand the soil becomes dusty 

 in dry weather, and it becomes difficult to reap any benefit from it. 

 With less than 30 per cent, of sand, the very clayey soils are still fitted 

 for the cultivation of oats. When the proportion of sand is 30 per cent, 

 barley raised is better than wheat. 



THE CHEMICAL PROPERTIES OF SOIL. 



A knowledge of the chemical composition of a soil is often of great 

 benefit to the farmer, as allowing him to judge whether it contains the 

 proper soil-constituents of which the crops he proposes to raise stands 

 in need, or, being deficient, what is likely to prove the best fertilizer to 

 be applied. Mere analytical results do not, in a great many cases, show 

 the agricultural capabilities of a soil ; thus, there are many soils whose 

 chemical composition is apparently similar, that is to say, that the nu- 

 ll AG— '86 



