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For polychromatic prints the operation must be carried on as above, using a neutral grey dye, and the colour may be applied in the required places. The colouring matters employed by M. Lemary are either aniline or vegetable. The process consists in the dye soaking into the organic substance with which the paper is sized, and penetrating more or less according as it is influenced by light. M. Louis Chamussy's Printing Process.—M. Louis Cha- mussy has indicated a new method of printing silver photo graphs. Glasses are prepared, such as are used by photo graphic enamellers, with great care, and afterwards plunged in an albumen bath, chlorinated according to its richness and density and the depth of tone desired. The different chlorides used produce varied results. For brown blacks, chloride of ammonium should be employed. Red tones and purple blacks are obtained with chloride of strontium. Chloride of sodium gives blue blacks. Bi chloride of mercury, notwithstanding its tendency to pre cipitate a portion of the albumen, gives vigorous metallic black tones. The chlorides of zinc and sodium also pre cipitate the albumen, but in certain cases they may augment the rapidity. The proportion of these chlorides may vary from one to seven, or even eight per cent. The albumen- ised glasses are drained, put up to dry, and after being well aired, they may be preserved in boxes or packets out of the damp. To sensitize them, they are placed in the silver bath, the strength of which may vary from ten to twenty-five per cent., according to desired effect. The plates may remain in the bath from five to twenty minutes, then taken out and allowed to drain, wiped carefully on the wrong side, and left to dry. The printing of these glasses is similar to that of albumenised paper; as soon as it is judged from the back of the glass that it is sufficiently printed, it may be taken out and replaced by another. The fixing is accomplished with a five per cent, solution of sulphocyanide of ammonium ; it takes scarcely half a- minute, and must be washed carefully for some minutes. Once washed and dried, the print may be retouched, if necessary. If it is desired to mount these prints on enamelled cards or other substances, warm gelatine must be used. When perfectly dry, these pictures are almost absolutely permanent. To finish them, the polish is rubbed off with pumice stone, and they are ready for use as stereo scopic slides. M. Chamussydoes not say how these prints may be transferred from glass to paper. In such a case, the glass must first be coated with some isolating substance, as talc, ox-gall, &c. Gustave Dore.—One of our great artists has been taken from us. Gustave Dore has left behind him an immense work; above all, his illustrations to numerous books by which he has achieved his fame, and which may be counted by the thousand. It is a grievous thing to state that, of this gigantic labour, there does not exist a single original design ; all these drawings executed on wood have been cut ' and interpreted by the graver, and the personality of the 1 artist has been lost in that of the engraver, so that only ' the modelled mask of the reality is presented. It is to ' be regretted that the following simple device was not re sorted to : the publishers desiring Gustave Dore to execute 1 his designs on paper, might have photographed them on I to the wood, so that the originals would not be touched, * and their value to-day, as precious mementoes of a great I artist, would be considerable in museum collections, &c. 1 Publishers engaging talented artists should note this: the ’ original design itself will compensate for the amount ! paid to the artist and engraver. Leon Vidal. NOTES ON PHOTOGRAPH. BY E. HOWARD FARMER. Lecture X.—The Gelatine Process—Continued. Alkaline Development (continued).—The practical lessons learnt last week may, for the purpose of remembrance, be put together briefly, thus— 1 1st. That pyrogallic acid is the developer proper, since it a will produce an image alone ; but that a certain quantity s of ammonia is required to be present, in order to obtain . sufficient density. 3 2nd. That ammonia, besides giving density, acts as a ; powerful accelerator by increasing the affinity of the pyro gallic acid for oxygen. 3rd. That potassium bromide acts as a retarder, prevents ■ fog, and produces greater contrast. 4th. That sufficient (and no more) ammonia should be i present to bring out the requisite details, and that the i density should be regulated by increasing or diminishing ; the quantity of pyrogallic acid. • 5th. That in cases of under-exposure the ammonia should be increased, and the potassium bromide diminished, as far ' as possible, without producing fog ; and in cases of over- exposure, the ammonia should be diminished, and, if neces sary, the bromide increased. As regards a working formula ; to those who are not satis fied with the one they are using, I would recommend Mr. Edwards’ developer, which is made as follows :— No. 1.—Pyrogallic acid 1 ounce Glycerine ... 1 „ Methylated alcohol 6 ounces Mix the glycerine and spirit, and add the pyrogallic. No. 2.—Potassium bromide ... ... 60 grains Ammonia ’880 ... ... ... 1 ounce Glycerine ... ... ... 1 , Water 6 ounces To make the developer, add one part of No. 1 to fifteen parts of water, and label this bottle D (developer). In another bottle mix one ounce of No. 2 with fifteen ounces of water, and label it A (accelerator). To develop a plate, mix equal portions of D and A, and pour them (avoiding bubbles) steadily over the plate, placed in a shallow dish. Rock the dish gently, taking care to keep the plate well covered with the solution ; when, if the exposure has been correct, all the detail will be out, and the development complete in about one minute. If the image fl ashes out, showing over-exposure, the mixed developer is at once thrown off, and the plate flooded with D alone, which will check the development, while the image grows in density. Under-exposure can be corrected to a great extent by increasing the proportion of A in the deve loper. It will be noticed in this developer that the quantity of bromide is very small (+grain to ounce, nearly), that the density is regulated by the pyrogallic acid, and errors in exposure by ammonia, which methods we found last week to be the best. It must not be supposed that this developer of the strength here given is suitable for all kinds of plates, which is by no means the case ; for instance, in many cases the proportion of pyrogallic acid will be found too large. To obviate this difficulty, either the same kind of plates should always be used, or, in using afresh kind, the proportions of the ingre dients should be altered to suit. Sulphite of Soda.—Some time ago Mr. Berkeley recom mended the addition of this substance to a pyrogallic develo per for the purpose of preventing the objectionable yellow stain which frequently occurs in negatives. For this pur pose he directs that in making the pyrogallic solution, four times its weight of sulphite of soda should be dissolved in water and neutralized with citric acid, and in this is dis solved the pyrogallic; the solution thus formed keeps indefinitely. The reason of its efficiency does not appear to be known with any degree of certainty ; possibly in oxidizing the pyrogallic acid forms a colourless soluble compound with the sulphite. Ferrous Oxalate Development.—This consists of treating the plate with a solution of ferrous oxalate in potassium oxalate, a small quantity of potassium or ammonia bromide being usually added as with pyrogallic development. It was first introduced by Carey Lea in 1877. Potassium Oxalate K:(C,0,).—There are two principal