A Manual Of Photography

BROMIDE OF SILVER AND MERCURIAL VAPOUR. 8/ of a taper onlv. The nitrate of silver must now be removecl from the paper by well washing in soft water to which a small quantity of salt has been added, and it should be after- wards soaked'in water only. When the picture has been dried, wash it quickly over with a soft brush, dipped in a warm solu- tion of the hyposulphite of soda, and then well wash it for some time in the manner directed for the ordinary photographs,. in order that all the hyposulphite may be removed. The drawing is now fixed, and we may use it to procure positive pictures, many of which may be taken from one original. The transfers procured from tins variety of negative photographs have more decision of outline, and greater sharpness in all their minute detail, than can be procured by any other method. This is owing to the opacity produced by the curious combination of mercury and the bromide of silver, which is not, I believe, described in any chemical work.. This very beautiful process is not without its difficulties ; and the author cannot promise that, even with the closest atten- tion to the above directions, annoying failures will not occur. It often happens that some accidental circumstance, generally a projecting film, or a little dust, will occasion the mercurial vapour to act with great energy on one part of the paper, and blacken it, before the other portions are at all affected. Again, the mercury will sometimes accumulate along tlie lines made by the brush, and give a streaky appearance to the picture, although these lines were not at all evident before the mercurial vapour was applied. The action, however, of this photographic preparation is cer- tain ; and although a little practice may be required to produce finished designs, yet very perfect copies of nature may be effected with the greatest possible ease and certainty. I have stated that the paper should be placed wet in the camera: the same paper may be used dry, which is often a great convenience. When in the dry state, a little longer exposure is required, and instead of taking a picture in four or five seconds, two or three minutes are necessary. I cannot conclude without remarking, that it appears to me that this process, when rendered complete by the improvement of its manipulatory details, will do much towards realizing the hopes of those who were most sanguine of the ultimate perfec- tion of photography ; and will convince others who looked upon the art as a philosophical plaything, that the real utility of any discovery is not to be estimated from the crude specimens pro- duced in its infancy, ere yet its first principles were evident to those who pursued it with an eager hope.