38 The American Geologist. January, 1905 
made use of in this instance is known as Brogger's modifi- 
cation of Harada's apparatus. It consists of an elongated 
pear-shaped glass vessel closed at the top with a ground 
glass stopper and provided with two glass cocks, one about 
midway the length of the vessel and another near its bottom 
end. 
Some experiments were first made to ascertain the 
necessary fineness of crushing and the losses in fine powder. 
By carefully crushing in a steel mortar (not pulverizing) a 
small sample of the Palisade diabase to pass a 20-rfiesh sieve, 
and then washing out the fine dust that would float indefin- 
itely in water, a loss of nearly four per cent was sustained. 
At this mesh the minerals were very imperfectly separated. 
Crushing to 40-mesh nearly tripled this loss. The Red Hul 
syenyte treated in the same manner gave a loss at 20-mesh 
of but two per cent. While at 40-mesh this was increased 
to quite 10 per cent. After washing out the flour, an anal- 
ysis of the 20-mesh rock gave. — 84.75 P^r cent of the light 
colored minerals, orthoclase, nephelite and sodalite, and 15.25 
of hornblende. The 40-mesh rock gave, — 81.35 of the light 
colored minerals and 18.65 o^ hornblende. These figures 
would indicate a more than proportional loss of the lighter 
constituents. 
It was found that with the Westerly granite a fair de- 
gree of separation was accomplished by crushing to 40-mesh, 
without a loss of over four per cent in fines. This w^as pos- 
sible only with extreme care in crushing and by constant 
screening of the crushed material from the mortar without 
permitting any considerable portion to accumulate. The 
rock was first hammered to about pea size and only a few 
pieces put into tlie mortar at a time. After screening it was 
washed by stirring in water, allowing to stand, then decant- 
ing. 
In the present experiments, mineral fragments were 
used for indicators and were obtained from the granite itself. 
A few grains of each of the minerals to be separated were 
placed in the solution which was then diluted till the lighter 
rose and the heavier ones sank. If the specific gravities of 
the two were near to each other the point of separation 
