Report of Sub -Committee. 
39 
peiitine in a clean bottle^ and when the specimen has been a 
day or two (perhaps a longer time may be required for some) , 
it can be mounted in the chloro-balsam^ as I have described 
above. 
Refractory specimens^ or those which are very oily^ may, 
after immersion in sweet spirits of nitre, and cleaning in tur- 
pentine, be again soaked in sweet spirits of nitre, when the 
turpentine will be expelled. If they are then a second time 
taken out of the sweet spirits of nitre and plunged in turpen- 
tine, the clearness of the globules which escape will indi- 
cate if the specimens are sufficiently cleansed. Mem. The 
sweet spirits of nitre must be fully expelled, or the Canada 
balsam will assuredly quarrel with it, and form a cloud round 
the object. 
I am modifying the above plan by using sulphuric ether 
dissoh^ed in three times its bulk of spirits of wine. 
I inclose three specimens for the acceptance of the Society, 
with four slides, illustrating that part of the paper on perfo- 
rated slides for mounting objects. 
No. 1, is a slide done with abroach. 
No. 2, a further stage, with the additional use of one 
file — both done in eight minutes. 
No. 3, a completely finished, perforated slide. 
No. 4, a cell cut out of a portion of a slide, and roughly 
mounted. 
Report of the Sub-committee of the Microscopical Society 
on the Best Form of Universal Attachment of the 
Object-glass to the Body of a Compound Microscope. 
(Read November 12th, 1857.) 
The practical inconvenience that has arisen from the 
adoption, by difi'erent makers, of various modes of attaching 
object-glasses has long since been universally admitted. 
In recommending a form of attachment for general adop* 
tion, it appears necessary to consider the following conditions : 
1. That the greatest amount of truth be ensured, both in 
the centering and in the parallelism of the axes of the body 
and object-glass. 
2. That the linear aperture be large enough to transmit 
all the pencils that can fall upon any field- glass in ordinary 
use. 
