246 The Philippine Journal of Science 
surface of the liquid without undue stirring or agitation. Sev- 
eral days are required for concentration of the glycerin. Too 
rapid concentration causes shrinkage of the specimens. Passing 
the air admitted to the bottle through calcium chloride tubes 
and a sulphuric acid gas drier does not materially accelerate 
the evaporation. 
When smaller quantities than 2.5 cc of material are to be 
treated, the specimens in dilute glycerin are placed in a cylin- 
drical vial about 23 mm wide and 80 mm deep, which is filled 
to a depth of about 70 mm. This vial is then placed in the larger 
bottle so as to stand under the air jet. When used in this way 
the larger bottles are provided with a floor of paraffin, which 
is melted and then cooled while the bottle stands on a level sup- 
port, to give it a flat, level surface. 
The use of an aspirator or aspirator pump for providing the 
air blast is yet to be tried. 
A METHOD FOR MAKING SEALED GLYCERIN MOUNTS 
Sealing mounts in concentrated or dilute glycerin presents a 
difficulty that does not occur in the use of aqueous media, which 
on evaporation leave the cover and slide surfaces dry; namely, 
the impossibility of securing contact of the cementing medium 
with glass surfaces which have become coated with a film of 
the nonvolatile glycerin. And, further, owing to its hygroscopic 
property, the glycerin takes up atmospheric moisture through 
the least crevice, expanding, and exuding in damp weather, and 
evaporates, contracting, and drawing air under the cover, until, 
after the seasonal changes of several years, slides defectively 
sealed are likely to become completely dry. This difficulty can be 
obviated by using a cement which is readily freed from a glycerin 
coat and providing contact of the cement with the glass surfaces 
before the glycerin is applied. 
I have made mounts of the larger Volvocaceae, which require 
considerable space between slide and cover, and these are in 
good condition after three years. The cement used is an alco- 
holic solution of shellac. It is applied with a brush. The 
method will now be described in detail. 
Orange flake shellac is prepared by covering it with 95 per 
cent alcohol and allowing it to stand for several days. If the 
resulting solution be too thin it is allowed to evaporate partially ; 
if too thick more alcohol is added. A camel’s hair brush for 
applying the shellac is inserted in a perforated rubber stopper 
of a bottle of 95 per cent alcohol, in which it is kept when not 
in use. 
