PHOTOGRAPHY. 
63 
containing pjrogallic acid, ammonia, and potassium bromide. The 
excellence of the result largely depends on the due proportion between 
these constituents, and here more experience is perhaps necessary than 
in any other part of the process. The image having been fully developed, 
the plate is well washed, and then immersed in a solution of alum, which 
hardens the film. After another thorough washing it is “ fixed ” by 
immersion in a solution of sodium hyposulphite, which dissolves out the 
unchanged bromide of silver, and being once more well washed it is 
finished, and must be set up in the rack to dry spontaneously. On no 
account must heat be applied, not even the warmth of sunlight, or the 
film will melt. When dry it must be varnished to protect the film. The 
printing operations are best deferred till the return home, as they would 
involve the carriage of a large amount of extra apparatus. It is generally 
best to get the printing done by a professional printer; but if the 
traveller prefers to print from his own negatives he will find full in¬ 
structions in 4 The Art and Practice of Silver Printing/ by Robinson and 
Captain Abney. 
As regards the expense of a photographic outfit, such as that described 
above, the following may be taken as average prices for the largest size 
recommended, namely, for plates x 5 inches:— 
Camera, 6 to 8 guineas. 
Double slides, about 1 guinea each. 
Lenses, as described above, No. 1, Ross new lens, replacing the Rapid 
Symmetrical series, 3 1. 5s.; No. 2, 3/. 10s.; No. 3, 3/. 15s. 
The above may be arranged to pack into a solid leather case, con¬ 
veniently in the form of a knapsack, measuring about 16 in. wide, 12 in. 
high, and 5 in. deep. This can easily be carried on the back of one man, 
and is of a more convenient shape than the cases generally sold for the 
purpose. 
Tripod stand, 25s. 
Lantern, from 2d. to 10s. 
Gelatine plates, about 3s. per dozen. 
Apparatus and chemicals for development, about 15s. 
Total, exclusive of the plates, about 25?. 
The plates and other apparatus, with the exception of the knapsack 
and its contents, and the tripod stand, are best packed for travelling in a 
strong basket, which is much better than a box, being more elastic and 
