148 ANNUAL REPORT 
For quartz with a specific gravity of 2.64, ¢==100.4, a=0.903 and 
C—0.5195. 
R. H. Richards* gives the following values for the velocity of the 
fall of quartz for various coarser diameters: 
1] 
Diameterinsmmesee see ORGS FOR22 2 Se O0ns3e Ono | 0.8 1.36 
~ 
A. satisfactory method of carrying out this sedimentary analysis is 
given by Osborn,” who makes three separations of particles ranging from 
0.25 to 0.05 mm., 0.05 to 0.or mm. and from 0.01 mm. diameter to fine 
dust. He uses a sample of 30 grams and passes the material through 
sieves. For carrying out the work he simply places the sieved material 
into a beaker, adding water and allowing the sediment to settle a short 
time. : 
“The turbid liquid is then decanted from the sediment and after 
standing until a slight deposit has formed is again decanted and the 
sediment examined with a microscope. If sand (0.25 to 0.05 mm.) is 
present, the subsidence of the turbid liquid 1s continued until no more 
sand is deposited. As the sand subsides rapidly there is no difficulty in 
altogether freeing the liquid first decanted from this grade of particles. 
The sediment thus obtained contains all the sand, a part of the dust 
(0.01 mm. and finer) and much silt (0.05 to 0.01 mm.). As only dust 
and the finest silt render the water turbid, the sediment is stirred a few 
{imes with a fresh quantity of water and decanted after standing long 
enough to let the sand settle. When the water is decanted free from 
turbidity, the last portions passing through the sieve with clear water 
are added to the sediment and the decantation continued so as to 
remove most of the silt. When no more silt can be easily removed from 
the sediment without decanting sand, the decantations are made into a 
different vessel and the subsidence so timed as to remove as much of 
the silt as possible. 
“By using a little care at least three-quarters of the sand are thus 
obtained free from silt. The rest of the sand is mixed with the greater 
part of the silt, which has been decanted into the second vessel. The 
size of the smallest particles in this vessel is determined with the micro- 
scope, to make sure that its contents are free from dust, as they usually 
will be if, after settling for a few moments, they leave the water free from 
turbidity. 
“The material is thus separated into three portions, one containing 
sand, one sand and silt, and the other silt, dust and impalpable powder, 
1O0re Dressing, p. 469. 
2H. W. Wiley, Agricultural Analysis, p. 196. 
