OF DENISON UNIVERSITY. 
125 
quires the proper consistency before each mounting, in a spoon, but 
there are many objections besides the tedious process involved. When 
any number of slides are to be made there is economy in having bal- 
sam of the proper sort at hand and if some becomes brittle it may be 
melted with some which is yet too fluid. It is desirable also to per- 
form the same part of the process with a number — say a dozen — sam- 
ples at once, as it saves time and the chances of accident are fewer, 
provided care be taken to avoid loosing the identity of the specimens. 
After the chip has been glued to the glass square the former is ground 
carefully with coarse emory of various grades until the section shows 
signs of falling to pieces, it is then put upon the flour and slime plates 
in succession. Great care must be used to prevent the accidental 
mixture of coarse emery or gritty grains with the emery flour or slime, 
as one grain of coarse grit may suffice to destroy the section just when 
completed. When the section is judged thin enough, it is proved 
by cleaning the square and laying it over print which should be clearly 
seen through the section. The superfluous and soiled balsam is care- 
fully cleaned away from the section and it is placed on the heating 
table on which are also laid the slip and cover glasses. When the bal- 
sam is fluid, a small fragment of somewhat more fluid balsam than that 
previously used is placed on the glass slip and the thin section is 
pushed off the plate glass square with a blunt needle, the cool needle 
adheres to the section and the latter is removed to the now perfectly 
fluid balsam on the glass slip. The warm cover glass is now quickly 
placed over the section which has been completely immersed in the 
medium. Care must be taken that a sufflcient quantity of balsam is 
used to completely fill the space between the slip and the cover and 
also that no bubbles arise to obscure the field. If all has been suc- 
cessful the spring clips are applied and the slide is placed aside to dry 
without attempting to clean away the superfluous balsam. In a day 
or two this will be hard enough to be readily removed with a knife and 
the slide may be cleaned with a soft cloth wetted with alcohol, care 
being taken that the balsam under the cover is not attacked by the al- 
cohol. The slide is then ready to label in any convenient way, the 
number of the corresponding hand sample being in every case attached 
to the slide. 
The process above described is less tedious than might be supposed 
but can be materially shortened by the use of a lithological lathe pro- 
vided with lead and iron horizontal laps. The accompanying wood 
