36 PREPARATION AND MOUNTING 
Mr. Spencer slightly modifies the above, using wood 
jaws and wedge, which the following engraving will best 
explain. 
DR. MATTHEWS’ TURNTABLE, TWO-THIRD SIZE. 
Many objects for the microscope may be seriously injured 
by allowing the fingers to touch them—many more are so 
minute that they cannot be removed in this way at all, and 
often it is necessary to take from a mass of small grains, as 
in sand, some particular particle. To accomplish this, there 
are two or three contrivances recommended: one by means 
of split bristles, many of which will readily be found in 
any shaving-brush when it has been well used. The bristles 
when pressed upon any hard surface, open, and when the 
pressure is removed close again with a spring; but the use 
of these is limited. Camel-hair pencils are of great service 
for this, and many other purposes, to the microscopist. 
In very fine work they are sometimes required so small that 
all the hairs, with the exception of one or two finer pointed 
