4 THE MICROSCOPE. 
and shake it until you are tired; allow the material to settle until the 
microscope shows that all the diatoms have sunk, siphon off the 
water and renew it, adding the few drops of ammonia, and repeat 
until all clear, always replacing the filtered with distilled water in 
the last three or four shakings, 
It has been said that no amount of cleaning can take the place 
of making a clean collection. Whether this is true or not, and I am 
inclined to think it is not, the alternative of a poor collection is fre- 
quently none at all. By the above method, the most refractory 
recent gathering can be subdued. A fossil deposit would require 
very different preliminary treatment, but the method of removing the 
sand holds equally good. 
Concerning apparatus, if it is expected to make the diatoms 
perfectly clean, the tools must be perfectly clean. The siphon should 
be thoroughly cleansed before using and before putting away. The 
pipette should receive particular care. The rubber bulb should be 
removed. turned inside out and washed, and all vessels used in the 
latter stages of the process should be chemically celan. Glass stop- 
pers for the shaking bottles should be used instead of cork, and while 
the diatoms are exposed, all unnecessary bustle should be avoided in 
the room, as dust is ever present. 
As a mounting medium for general use, I have seen nothing 
superior to styrax properly prepared, and for cement nothing better 
than hard-oil finish, sold in the paint stores for a dollar and seventy- 
five cents a gallon. This, with the addition of finest dry lampblack, 
makes a black cement that is not excelled. 
A slide of diatoms cleaned in the manner described, mounted in 
styrax and ringed with hard-oil finish, followed by hard oil finish 
with lampblack, will, I am sure, be submitted to criticism with a 
feeling of perfect confidence. 
TAYLOR’S COMBINATION MICROTOME. 
THOMAS TAYLOR, M. D. 
HIS microtome is adapted to three methods of section-cutting. 
The instrument is of metal, screwed to a block of polished 
mahogany. (A) is a revolving table with graduated margin, in 
the center of which is fitted a freezing box (x), having two projecting 
tubes, one to admit freezing water and the other as an outlet for it. 
The water is supplied from the reservoir, and carried off by means of 
rubber tubing attached to these metal tubes, the terminal end of the 
