102 
Journal of the 
cells in use are liable to the same fault, and wax cells not more 
than any others. He considers that the mistiness may sometimes 
be caused by emanations from the wax, “ but that it more 
frequently results from the use of cements containing resinous or 
oily solvents, like turpentine or benzole f while, of course, if tlie 
object be not quite dry when mounted, the water contained in it 
will be liable to condense upon the cover ; and he says that, “ if a 
cement is used composed of shellac dissolved in alcohol, plenty of 
time allowed for the completion of each step, and the specimen 
thoroughly dry, the cell will be free from vapour and 
condensationsand he thinks, therefore, that the wax cell is “the 
best cell for dry objects that has ever been used.” Mr. Stidham 
“ has found no trouble since covering the whole cell with a thin 
film of shellac, and using shellac to fix the cover, provided the day 
ivas a dry one” and the cover is held for a moment over the lamp 
flame. He thinks Mr. C. C. Merliman’s suggestion of leaving a 
small opening so that moisture may get out would be of practical 
advantage if it could be done. 
It seems to be the general opinion that shellac is the best 
cement for dry cells, and Dr. H. L. Smith strongly recommends 
the use of cells made of paper saturated with it, and allowed to 
dry, and having the covers fixed by passing a hot wire round the 
margin. He remarks that this process is so simple that it is 
strange no one has thought of it before, but there are probably 
few microscopists who have not made use of paper cells saturated 
with cement; but in common with many others, I have used 
balsam or gold-size for the purpose, which, it now appears, has 
been to a great extent the cause of the dew on the cover. If 
shellac is less liable than other cements to give off emanations, it 
matters little what substance the cell is composed of, provided 
that it is completely coated inside with a film of shellac. It is to 
be noted, on the other hand, that Dr. Phin finds that shellac, in 
all its pure forms, is very apt to leave the slide after some time. 
The above-quoted suggestion, that a small opening should be left 
for the escape of moisture, can be carried out without any 
difficulty. I have often affixed the cover to the cell by touches of 
cement in two or three places only,\ith good results as long as 
the cell remained in this condition : but when, fancying that the 
cell was sufficiently dry, I have allowed a fluid cement to run into 
