
128 THE NORTHERN MICROSCOPIST. 

g. Re-float in a beaker. 
to. Dry again, after which they are ready for mounting. 
—Chas. Elcock, in J. Post. Mic. Soc. 
CoLLectinG Diatoms.—Amongst the few localities (says Mr. 
Partridge in the “Journal of the Postal Microscopical Society”) near 
Stroud, in which I have collected are :— 
Stroud Upper Reservoir—Cocconema and Pinnularta. 
Seven Springs, Bisley—D. vulgare and Gomphonema. 
Salmon’s Springs—Syzedra radians, nobilis, etc. 
Stratford Mill Pond—Swuvirella and FPleurosigma. 
Lightpill— Cocconema lanceolatum. 
Pond, Bowbridge—VPleurosigma, etc. 
Heven’s Spring—WVavicula. 
THE APERTURE SHUTTER.—Mr. W. H. Bulloch, the well-known 
manufacturer of microscopes at Chicago, has informed us that it 
is now more than five years since he adapted the iris diaphragm 
as a nose-piece to his microscope, “for reducing the angle of light 
in the instrument.” This is perfectly true, and several other 
catalogues mention the fact of an iris diaphragm adapter being in 
existence. 
Our connection with the “aperture shutter” is simple enough. 
We tried to prove to the microscopical public that wide angle 
objectives would give penetration when properly used. All an- 
tagonists to wide apertures revelled in the argument that such 
objectives did not possess this attribute, and histologists were 
advised to sacrifice the finest definition to good penetration. ‘This 
called into existence two classes of objectives, and there is but 
little doubt that this demand for two glasses in the place of one, 
retarded the general introduction of wide apertures. 
We wish to give opticians every credit due to them, but to Prof. 
Abbé entirely belongs the credit of demonstrating that penetration 
could be secured by reduction of aperture; and we are unable to 
find any account, before our own, that wide angle objectives could 
be made to yield penetration under any circumstances. 

BroLocicaL APPOINTMENT.—There is some talk of Mr. Patrick 
Geddes, a Scotch biologist, who has recently attracted con- 
siderable notice by special discoveries, being appointed to the 
Chair in University College, rendered vacant by the transference of 
Prof. Ray Lankester to Edinburgh. Nothing is settled, however, 
and several of the younger and more eminent Cambridge biologists 
may be expected to enter the field. 
Our VERIFICATION DEPARTMENT.—We have heard that dealers 
in microscope objectives have expressed opinions that this depart- 
ment is “not infallible,” and that “angle is only a secondary 

