MICROSCOPY. 373 
by turning the milled screw till the point of the needle (which 
should be very fine, or a bristle may be used if preferred) touches 
the object, give it a few backward turns to lift it clear, then more 
rapidly by means of the coarse adjustment of the microscope ; 
substitute the stage plate with the cover attached to it by some 
kind of cement and carry the plate, by means of stage movement, 
so that the object may be let down in the required position on 
the glass cover. Another may then be placed beside it, etc. 
After completing the arrangement, moisten the glue by breathing 
upon it or holding in the vapor of distilled water, though the 
latter is liable to wash the objects out of place unless dextrously 
managed. They are then secure and will sometimes bear rough 
Usage in mounting without becoming displaced. Occasionally 
there will be a specimen that will adhere to the needle so persis- 
tently that we are liable to consider patience no longer a virtue. 
In such cases try another specimen, as different diatoms of the 
same species vary greatly in grade of difficulty. My experience 
is that discoid forms are most easily arranged and the light Navi- 
cule the most difficult. Sometimes air prevents the balsam from 
entering the frustule, which may be avoided by separating the 
valves of such as will admit of it, when time is of no consideration. 
Thus any one of the requisite mechanical tastes can have slides 
of diatomacee arranged in squares or otherwise to suit the fancy, 
and a large number of specimens be examined without change of 
slides. The finest specimens’ may be thus secured, from impure 
gatherings, and reference made to any particular specimen without 
the use of the “ finder.” —W. W. River, Greene, Iowa. 
Histotogy.— Dr. James Tyson’s magazine article, narrating his 
experience in the laboratories of Dr. Klein of London and of Prof. 
Stricker of Vienna, has been raised to a little book and published 
by Lippincott as an Introduction to Practical Histology. The 
additions to the original article are not extensive, but are designed 
to make it more comprehensive and more available as a hand-book 
for actual beginners in histology. While almost every microscop- 
ical treatise is full of mounted objects and mounting objects, it is 
refreshing to find even a small work which says hardly a word 
about either, but devotes itself entirely to microscopical study. 
Like most histologists, the author values highly the vertical use 
of the microscope, and says little of the binocular instrument. 
