II.] 



ANAL YTICAL METHODS 



53 



nated " fine silt," and lies between ooio and 0002 mm. 

 in diameter. 



5. The sediment remaining in the beaker is worked 

 up afresh just as in the previous operations, the mark 

 being now placed 10 cm. from the bottom of the beaker, 

 and the time of settlement fixed at one hundred seconds. 

 The sediment is dried and weighed as " fine sand," while 

 the portion that is poured off is obtained by evaporation 

 as in the previous operations, and is designated as " silt." 

 The soil has thus been divided into the following series 

 of fractions : — 



If there be much " fine gravel " in the soil, it is best to 

 make a separate determination of its amount on a 

 sample weighing 50 grams, treating with acid as before, 

 and then washing the whole on to the 1 mm. sieve. 

 The result obtained should be taken as the true 

 percentage, and the other percentages found in the 

 analysis of 10 grams only should be recalculated to agree 

 with it. 



The sizes of the particles, the depth of the liquid, and the 

 times adopted above, are purely conventional. The time 

 of settlement required to obtain a fraction of any 

 given range of size can be determined by a series of 

 trials, the material remaining suspended in each case 



