73 
JULY 24TH. 
MICROSCOPICAL MEETING.—DR. HALLIFAX ON 
“ CEMENTS.” 
All who had mounted objects for themselves had some objection to 
the different cements and varnishes recommended in the manuals on 
the Microscope. Against some the objection was that after a time 
they cracked and peeled off; others gave off exhalations which not 
only clouded the covering glass, but spoilt the object ; this latter fault 
belonged io all varnishes or cements containing oily substances. Dr. 
Carpenter, no mean authority, and one who had had considerable 
experience in the matter, advised that all valuable slides should be 
varnished annually to preserve them, thus showing, as the result of his 
experience, the untrustworthiness of the cements generally used. 
There was one cement, though recommended in books, against 
which, so far as his experience went, such objections could not be 
raised, viz., sealing wax varnish or cement. This arose, he con- 
sidered, from the nature of its composition, which, according to Ure, 
was 20 per cent. Canada balsam, 50 per cent. shell lac, the rest colour- 
ing matter, and a drop of Balsam of Tolu. A cement, formed by dis- 
solving the best sealing: wax in spirit he had used now for years, and 
found neither leakage, chipping, flaking, nor exhalations ; in fact, as far 
as his experience went, it was the most trustworthy cement he knew. 
Somelittletime since Mr. Wonfor showed him some slides which had 
been sent him by Mr. Curties, the cells of which consisted of con- 
centric rings of different colours ; some presenting, perhaps, a fancy 
appearance, but, at the same time, it struck him, they were composed 
of anew cement. After various experiments he came to the conclusion 
that Canada balsam was the basis of the material. It would be seen by 
the slides which he and Mr. Wonfor would exhibit, that if he had not 
produced what he considered an identical cement, he had obtained one 
of a perfectly trustworthy character. Hehad mingled with the Canada 
balsam different pigments, and should it be objected that litharge added 
to gold size made it more untrustworthy, he might remark that gold 
size was an oily preparation, while Canada balsam was not. 
Canada balsam was the simplest, purest, most manageable, and best 
working of all media in which to mount objects, and if it could be 
made workable with a brush it would then become a cement. Now, it 
was known to be soluble in various substances—such as ether, chloro- 
form, and turpentine, none of which, from various reasons, he should 
