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top light from the lens is almost indispensable in the 
tropics. 
With regard to the vexed question of plates versus films 
the matter resolves itself into a consideration of portability 
and climate. Provided the climate is dry, films may be used 
with safety, but in a damp tropical climate it is safer to use 
plates, and the increased bulk, weight, and danger of 
breakage must be faced. There is no reason why fairly thin 
glass should not be used, at all events for quarter-plates. 
Halation is certainly minimised by backing, and it is 
advisable to have all the plates backed by the maker. 
A thick emulsion is desirable ; if this is very thick the 
plates need not be backed. If only one kind of plate is 
taken out, a sufficiently rapid brand for snap-shots should be 
selected ; should two kinds be taken, the second might be 
“ slow 55 for time exposures, and these might very well all be 
orthochromatics. In any case a few orthochromatic plates 
should be taken so as to enable a certain class of work to be 
done which ordinary plates cannot accomplish. Ortho¬ 
chromatic plates are somewhat difficult to work in the 
field, and opinions differ as to their keeping qualities. A 
yellow screen with ordinary plates might suffice for many 
purposes. 
The plates should be packed by the maker in tin boxes 
that will hold six dozen glass plates ; it is more convenient 
not to have these soldered down, but to have a deep flange 
the outside joint of which should be protected by adhesible 
rubber stripping. Films packed in tin boxes without suitable 
protection are very liable to fog. 
Do not leave the purchase of the photographic equipment 
to the last, but practice with the camera, the plates intended 
to be used, and the developer some time before starting, so as 
to be thoroughly conversant with the tools. If possible 
develop all the plates on the field so as to have the chance 
of replacing failures, and further, developed plates keep much 
better than exposed undeveloped plates. Alum is usually 
recommended for hardening the films when developing, for 
hottest climates an immersion of the plates in a 4 per cent. 
