244 
accustomed to use. To those to whom space and weight 
are considerations, the chemicals put up in tabloids by 
Burroughs, Wellcome and Co. are good and convenient. 
Some of the newer developers are also very portable and 
convenient, such as amidol, metol, and ortol, the first 
especially, as it works admirably with sulphite of soda 
only and is readily soluble in cold water. For hardening 
the gelatine coating of plates and films, and preventing 
frilling, commercial formalin, diluted to a strength of i part 
to 9 of water (i.e. i in io) is the best reagent. Formalin is 
also an excellent accelerator, and when added in the propor¬ 
tion of 2i=r minims per ounce of developer renders the use of 
an alkali unnecessary, and at the same time hardens the 
gelatine so that a special hardening bath is not required. 
This is especially convenient in climates where it is difficult 
to get the water cold enough for photographic purposes. 
Photographing Natives .—The photographs of natives 
should give the exact full face and profile. These two 
views are best taken on one plate side by side, the full face 
being taken first on the left half of the plate and the profile 
view next on the right half. To do this the shutter or partition 
fitting into the back opening of the camera is inserted in its 
place and pushed to the right so as to cover the right half of 
the opening ; the lens is moved by the horizontal movement 
of the front of the camera to the left till its centre is opposite 
the middle of the left half of the opening, the sitter is focussed, 
the back with the plate inserted and the exposure made. 
The seat is then turned from right to left through an angle 
of 90° and adjusted, when the sitter will occupy a position 
at right angles to his previous position. The partition in the 
back of the camera is moved to the left, exposing the right 
half of the opening, the lens is moved to the right till it is 
opposite the middle of the opening, the sitter focussed, the 
dark slide inserted, and the exposure made. In each case 
nthe shutter of the dark slide is drawn fully out. The two 1 
exposures should be made for exactly the same length of 
time otherwise they will not develop equally. 
The photographs should be taken to scale. The best size 
