THE FIELD-GLASS 247 
your friends. Lots of cheap booklets giving all 
necessary instructions for the making, mounting, 
and exhibiting of slides are obtainable. 
Many subjects are best photographed under 
“control.” Snakes, lizards, frogs, toads, etc., can 
be secured in glazed cages having suitable back- 
grounds. Butterflies and moths are generally photo- 
graphed in captivity in their breeding-cages. Newts 
and fish may be put in narrow glass tanks, furnished 
with pebbles and weeds. Such tanks need not 
ordinarily be more than an inch and a half from 
front to back ; they must have clear glass front and 
back, and a simple apparatus enabling a continuous 
supply and exit of water will improve matters. A 
suitable background behind the tank is necessary. | 
in Plate 61, a, you have a picture of apparatus I 
use for photographing flowers, etc., by the control 
method. The camera is set on a sliding trolley, 
which is secured in the necessary position with a 
butterfly-bolt. There is an easel on which a suitably 
tinted background is fixed. The apparatus is put 
on a table near a window admitting light from the 
north. A white paper reflector is placed in such a 
position that it reflects light on to the specimen, 
and thus even lighting is obtained. I usually stop 
the lens down to aperture f/32, and in an ordinary 
light give from thirty to forty seconds’ exposure. 
The same apparatus is used for copying prints and 
illustrations, and also in photo-micrography ; it was 
made at home, and has become almost indispens- 
able. 
A good Field-Glass is of immense service to the 
naturalist, especially for the observation of birds. 
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