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FEBRUARY 6, 1885.] THE PHOTOGRAPHIC NEWS. 83 PHOTO-TINT BLOCKS BY MR. DALLAS. Now that processes for making printing blocks by photo graphic agency are attracting much attention, and the blocks themselves are being so largely used by publishers, it is desirable to place before our readers examples of the process which has been worked successfully by Mr. Dallas during the past fourteen years. Mr. Dallas terms his pro cess " Dallastint," and does not publish any details con cerning it. The first block is from a photograph of a cockchafer’s ANTENNA OF COCKCHAFER. antenna, the negative having been made on a wet plate by Mr. F. Greening, of the Royal School of Mines. The second block is a photograph of a modern Japanese ware, also made on a wet collodion negative. USE OF THE. ROYAL ARMS. The following list of photographers and opticians who hold warrants of appointment from the Lord Chamberlain, with authority to use the Royal Arms, has been published in the London Gazelle:— London. Photographers.—John Thomson, W. Downey, Hills and Saunders, Alexander L. Henderson. Opticians.—A. W. Dixey, Horne and Thornthwaite. Provincial. Photographer.—Henry Joseph Whitlock, Birmingham. Optician.—Alexander Alexander, Exeter. Scotland. Photographer.—George Washington Wilson, Aberdeen. Optician.—Thomas Wedderburn, Edinburgh. THE INTENSIFICATION OF GELATINE NEGATIVES. BY II. CHAPMAN JONES. The methods that are now available for the intensification of gelatine negatives leave little to be desired. The replacement of ammonia in the mercury-ammonia method by sulphite of soda has made a clean method still cleaner, a fairly quick method even more rapid, besides adding the advantages of greater permanency, and more certainty as to the final result. The use of the sulphite gives an image in metallic mercury, and this can be made a new starting point in the operations if necessary, for reduction (by a very weak cyanide of potassium solution*) or further intensification. This intensification of the mercury image is just as easy and certain as the intensifi cation of the original (or unintensified) silver image would have been by the uranium method; and if pushed to the end, the density obtained appears slightly greater in the former case. As each atom of silver gives an atom of mercury which has twice the reducing power of the original silver atom (for by the action of the uranium and ferricyanide a mercuric salt results), one would expect to get a double quantity of uranium ferrocyanide deposited by the double method of intensification, but the experi ment does not seem to justify this conclusion. A small increase of density is apparent, though perhaps this appearance is deceptive; however, experiment shows that it is certainly not less dense by the previous change of silver into mercury, and the chemistry of the changes indicates that the density ought rather to be increased. So that if a thin negative has to be dealt with, one can not go wrong in applying to it the mercury and sulphite method—this may bring it up to printing density ; if not, follow with the uranium method; and if this fails, it must have been a considerable error of judgment that led to any attempt to improve the original. The uranium intensifier is not appreciated as it ought to be, on account of its supposed tendency to fog; and if the formul® usually given for it are followed by the photo grapher who is not also a chemist, probably he will never get a clean result. The following observations on this and other allied matters may perhaps be useful to such. 1. The mercury solution may advantageously be a saturated solution, and, after use, poured back upon the excess of solid contained in the stock bottle. Rinse the negative after its application, but a thorough washing is of little advantage. 2. The sulphite of soda need not be so pure as is necessary when used in the developer. A fair commercial article is quite good enough. It may be dissolved in from five to ten times its weight of water. After dissolving, make the solution slightly acid with citric acid—sul phurous acid is better, and should be used if at hand. This prevents the possibility of any alkaline compound acting on the bleached negative in a similar way to ammonia. The same bulk of solution may be used for two or three or more negatives, but if the action flags, it must be reinforced or replaced by fresh. After use it must not be returned to the stock bottle. • Dr. Eder. See current Year-Book, page 100.