60 
HINTS TO TRAVELLERS. 
a piece of iron over a fire.) Put on the lid and allow the plates to 
remain for an hour or more. Dry all the packing materials, remove the 
plates from the box and repack. The chloride will have absorbed the 
moisture in the plates, and rendered them quite dry and safe for preserv¬ 
ing for an indefinite length of time. The twin lens camera made by Boss, 
in its simple rigid form, is well suited for the work of the explorer. It 
consists of a stout body of thoroughly seasoned hardwood, not easily 
damaged by rough usage. The principal fittings required for adjusting 
the instrument are inside, protected by the outer case. The exception 
to this arrangement is the milled head by means of which the two lenses 
are focussed at the same time. The lenses are of uniform focal length, so 
that the image transmitted by the “ finder ” is a counterpart of the 
image which falls upon the sensitive plate. The advantage of this is 
that the object to be taken is seen on the finder-screen to scale exactly as 
it will appear in the finished photograph. By this means the operator has 
it in his power to place the object in the required position on the screen 
;at the moment of exposure. This is of signal importance if the object 
is moving about. It must also be noted that this form of camera may 
be used when the operator is facing at right angles to the object to be 
photographed. I have frequently found that natives of foreign countries 
resent the liberty taken of pointing a camera at them, and fly as if they 
expected to be shot. The slides are each made to hold two plates, or 
flat films. They are strong, serviceable, and easily managed, while the 
body of the camera is so arranged as to carry a roll holder. 
Apparatus and chemicals for development.—The development of the 
plates or films after exposure in the camera requires practice and experi¬ 
ence in order to secure the best results. Instructions for development 
are sent out with all cqmmercial plates or papers, but many failures 
would certainly result from attempting to work by these without some 
preliminary practice at home. As plates, &c., will keep after exposure 
{if well protected from damp) for 18 months, or longer if properly 
packed, it is not, of course, necessary to develop them en route , 
although if the traveller possess sufficient skill, and if ample water-supply 
and other facilities can be secured, it will be advantageous for many 
reasons to do so. On a long journey, when the temperature is not too 
high, use of convenient resting-places may be made to develop from time 
to time a few plates selected from the whole, both as tests for exposure 
