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280 THE NORTHERN MICROSCOPIST. 

followed that advice. I have used the microscope as a scientific 
tool, applied to hard work, and have found that all good work 
must be done with wide-angle lenses: the only drawback to their 
use is now removed by the introduction of the Aperture Shutter. 
Now as to photography, with which I am specially engaged. It 
has been said that a photograph, of a diatom, say, shows more 
than the eye can see in the microscope: that the Aperture Shutter 
does not improve penetration to the eye, although, in some mys- 
terious way, it may do so in photo-micrography. I have taken 
many hundreds of photo-micrographs, and let me tell those who are 
unacquainted with its methods this :—you can get in your photograph 
no more than your objective will show you on the focussing screen, but 
if not expert, you very often get ss. If your photograph does not 
give you a true picture of the object, as seen down the microscope 
tube, then your manipulation or apparatus is at fault. 
To give an example: lately I have been doing delicate work— 
photographing y,'55 of a grain of arsenic, using moderately high 
powers. Now I found, when examining the deposits, that I often 
could not get all the crystals into good focus at once. I knew that 
a good eye-focus meant a good photographic focus, and that it 
would be but a fool’s experiment to try to get a picture which would 
be in photographically good focus, when I had failed to get a good 
visual one. In minute photography the most exact focus is every- 
thing. So I tried the Aperture Shutter, and found that with it I 
could easily get all the crystals in good focus; the reduction of 
aperture was too small to spoil definition or illumination. As soon 
as I had got all the crystals in the field in sharp focus on the screen, 
I proceeded to take several negatives, using different lengths of 
camera to produce enlargements varying from 300 to 500 diameters, 
and all my photographs came out sharp and distinct, as I had seen 
them in the microscope and on the focussing screen. I have used 
the Shutter with a ,'; inch objective, both when examining and 
photographing “big” diatoms, and have found it simply invaluable. 
I have tested the Shutter severely, using it with objectives vary- 
ing from 5 inches to + inch focus, and have concluded that if any 
microscopist condemn it as a toy, then his microscope is probably 
one too—a toy he doesn’t know how to play with. 
I am, sir, yours, etc., 
J. H. JENNINGS. 
Sir, 
_ With reference to Mr. Miles’ paper, of which I suppose a 
notice will appear in your next issue, it would seem that the subject, 
by eliciting so little discussion, was uninteresting to the members. 
This is not so; but when “apertures” are spoken of, one’s whole 

