HORNBLENDE AND BYTUOWNITE FROM HYPERSTHENE GABBRO. 211 
Mineral Separation. 
The rock was crushed in a steel mortar and sorted by 
means of a set of sieves, those grains which were of the 
dimensions of the average grainsize of the rock, or slightly 
less than this, being chosen for separation. In this way 
apparently homogeneous grains of about the same size 
were obtained free from rock powder. These grains were 
partially separated by means of Klein’s solution (cadmium 
borotungstate) of specific gravity about 2°85, when the 
separation of felspar from the rest of the rock was almost 
complete. — 
Apparatus—An ordinary Brogger funnel was found to be 
the most convenient apparatus to effect separation. Wide 
glass tubing was drawn out and fitted with rubber tubing 
and a pinch-tap, but was found to be unsatisfactory as a 
separating apparatus for several reasons. The converging 
sides of the tubing tend to cause congestion of the grains 
at the lower end, besides which the grains are apt to 
adhere to the rubber tubing. When this resistance is over- 
come the liquid drops suddenly and disturbs the equilibrium 
of the floating fraction. The apparatus can separate only 
a very small portion of the rock at a time. 
A burette has the disadvantage of having too small an 
opening at the tap. The Brogger funnel, on the other hand, 
has a large opening and can separate a fair amount of 
material at one time, and yet is convenient to handle. 
Since it is made entirely of glass, with taps whose openings . 
are of the same bore as the funnel itself, there is no tendency 
for the grains to stick in any particular portion. Another 
advantage is that the central tap can separate the two 
fractions without disturbing the equilibrium of the floating 
portion. 
Heavy Liquids—Klein’s solution proved to be a con- 
venient liquid to use for the separation when the specific 
