108 NATURE TEACHING. 



MECHANICAL ANALYSIS OF SOIL. 



1. Separation of soil particles by means of 

 water : This operation may be conducted so 

 as to give quantitative results of interest 

 and value, if a small amount of apparatus is 

 procurable. For this work it is necessary to 

 have three sieves with apertures of known 

 sizes; brass sieves with circular perforations 

 are preferable to those of wire. A suitable set 

 consists of three sieves with holes of 2, 1, and 

 i millimetre respectively. (1 m.m. = ^ inch) 

 A small scale or balance for weighing the 

 separated gravel, sand, etc. is also required. 



2. With these proceed as follows: From 

 a well mixed sample of soil weigh out 50 

 grammes, (Ifoz.), stir this well with water in a 

 glass or cup and pour the water through the 

 sieve with 2 m.m. holes ; the sieve resting on a 

 dish or basin. With successive quantities of 

 water transfer all the weighed portion of soil 

 to the sieve. Gently wash the particles of 

 gravel by moving them about in the sieve with 

 a wooden rod or stirrer (or a glass rod tipped 

 with rubber) using fresh supplies of water until 

 the small stones are quite clean. Pour the 

 water and soil which has passed through the 

 ftrst sieve through the second similarly 

 supported on a basin, and the water and material 



