18 



An Italian chemist, M. Pellegrini, obtained the following results with 

 a clay soil oi Orciaiio, near Pisa, on using the apparatus named:* 



Noeble's. e8 - Masure's. 



Percent. Percent. Percent. 



Saiid .1 1.47 32.07 I 18.35 



Clay 87.31 37.67 71.90 



Earthy carbonates 20. 20 



Organic and volatile matter 9. 06 10. 25 | 



Undetermined I 14. 75 



Soluble and loss 1.56 



100.00 100.19 100.00 



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 alniqst a pure state, from the sand, lime, and other mate- 

 rials which accompany it. Masure's, and NoebJe's apparatus make use 

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

 more or less tine 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, iu 

 addition to that body, some very tine sand, some calcareous or felds- 

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

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

 riu, 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, be- 

 ginning 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 till 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 10 to 100 meshes to the 

 square inch, are sometimes used for this purpose, a weighed quantity of 

 soil being taken and the portion remaining on each sieve being col- 

 lected and weighed. 



* Peligot, p. 154. 



