SCIENTIFIC SUilMAEY 
529 
ture as lie proceeds in liis observation. It might appear at first that the 
lozenge-shaped aperture would interfere where certain varieties of illumina- 
tion are required ; but we think that this objection can only be urged in 
exceptional instances. Tor most of the purposes of research the new 
diaphragm is an immense improvement on the old one. 
Collins’ Graduating Diaphragm. 
A simple form of Achromatic Condenser, the invention, we believe, of Mr. 
Webster, and which was described some time since in Science-Gossip, is now 
undergoing certain modifications and improvements, which the manufacturer 
(Mr. Highley) thinks will render it equal in power to the common achromatic 
condenser, at a cost of about one-sixth of the latter. W e have not examined 
the instrument ourselves ; but from what has already been written, we appre- 
hend that it is a combination of the Kelner eye-piece and parabolic illuminator. 
A new mode of using the Lieberhuhn is suggested by Mr. Keneely Bridge- 
man. “ If,” he says, “ we cover up a portion of the reflecting surface of the 
lieberkiihn, we shall be enabled to obtain any proportion of oblique light in 
one particular direction ; and then, by rotating the Lieberkiihn upon the object- 
glass, may bring it to bear upon every part successfully without having to 
alter the position of the object. In this way the most delicate structure, 
such as the barbs upon the very beautiful and nearly transparent spines of 
Opuntia tunicata which are scarcely to be detected by the whole light, may 
be brought out into full and bold relief.” — Vide Quarterly Journal of Micro- 
scopical Science, xviii. 
Abstracts of papers relating to Histology wiU be found under the following 
heads : — 
Botany — 
A new species of Docidium. 
The Structure of the Vinegar Plant. 
