Volltext Seite (XML)
20 THE PHOTOGRAPHIC NEWS. LJANUARY 9, 1885. Sulphur must be dissolved in carbon bisulphide. Ihe best crystals are obtained in winter ; but at all times of the year the solution must be evaporated in a room quite free from draughts, and as cool as possible. These crystals 0 □ 4 0 0 © & 3 <0 a © Q Co 9 d oB o ft O p 9 o 0 0, Fo 4 °85 g Q fa e • e cD 0 % % Ca 3 CRYSTALS OF ARSENIC, FROM A DEPOSIT OF ‘002 GRAIN, CRYSTALS OF ARSENIC, FROM A DEPOSIT OF '001 GRAIN. must be photographed by reflected light with a low power. Salicin is a very favourite microscopic object; but the splendid discs usually seen on slides are only modifications of the typical acicular crystals. The real forms are best obtained from a dilute aqueous solution, which may be hot. If a little gelatine be added to the solution, delicate discs form on crystallization, which are seen to consist of needles radiating from a common centre. Fusion of the dry salt gives only coarse discs, but if a concentrated aqueous solu tion be made, and evaporated over a lamp until fusion just commences, very delicate discs of a larger size may be obtained. One method of obtaining fine discs is to put a solution of salicin in gelatine on a glass slip. Warm the slip over the lamp for a few moments, and then pour the solution off; enough will be left on the slide to form a thin film. The film is then pricked in several places with a fine needle, and immediately crystallization commences from each prick as a centre, and goes on all over the slide. The whole is at once covered with balsam and benzol, and a thin glass square gently pressed on. If not covered at once, the crystals become opaque. Santonin and phloridzin are crystallized from an alcoholic solution, and may be preserved in balsam. Here our Lessons in “ Photo-micrography ” are brought to a close. The student must once more be reminded that skill in manipulation of the microscope will not by itself produce the best results. There must be not only expertness in each photographic operation, but an intelligent under standing of the why of each process. Photography as a science must be studied by itself, and for itself; for it is only when an intelligent understanding, both of microscopy and photography, is gained, that photo-micrography be comes worth pursuing. FRENCH CORRESPONDENCE. Phototypes and Photographic Aqua-Tints—Colour SENSITONIETER—Experiments on the Sensitometer— Photographic Copyright—Poitevin Monument. Phototypes and Aqua-Tints.—I have, on several occasions drawn the attention of my readers to various photo- typographic processes which, for some years past, repre sent the results obtained by diligent workers in that direction, among whom may be cited—Ives of Phila delphia, Meisenbach of Munich, Angerer and Gschl of Vienna, Petit of Paris, &c. I spoke recently of a French process used by Boussod, Valadon, et Cie., late Goupil. The prints were indeed remarkably fine, but typographic reproductions of photographs do not give good results unless great care is taken in the printing, and this prevents the possibility of interspersing them with the ordinary type and printing at one time. In the studios at Asnieres, this difficult method has been replaced by another process, the printing of which may be entrusted to any good printer, and may be struck off at the same time as the text. This process, as worked by M. Manzi, resembles ordinary phototypes by the best method, inas much as a lined or granular surface intervenes to divide the high-lights from the shadows of the original. I have been examining at the office of MM. Boussod, Valadon, et Cie., the numerous specimens of this kind of photo engraving, and I never thought to have seen it reach such perfection; they are infinitely preferable to the previous work, presenting a granular aspect, brought out by this house. None of the work of the artist disappears in repro ductions by M. Manzi’s process. There are prints on view of considerable size and of grest beauty. 1 should not be surprised if all the work of this firm was not carried on by this method, as it gives so much life to the reproduced picture, and brings it out in such strong relief. To obtain this vigour, and preserve the brightness of the high-lights, recourse is had to two or three printings, by which the effect of a drawing in two or three tints is produce! The flatness of a monochrome is thus broken up. As I am quite incapable of moderating my enthusiasm excited by these prints, I can only recommend anyone doubting my veracity to inform himself at the publishers, and see if I may not be excused. M. Manzi has also invented a photo graphic aqua-tint process giving charming effects. The
