The Optical Magic Lantern Journal (March 1890)

The Optical Magic Lantern Journal and Photographic Enlargor, 75 them to one of the legs of the table or other support, for as the ends of the cylinders are not very broad, a little touch suffices to knock them over, and damage may be done by also dragging the lantern from its stand. to: Oxygen Cylinder Explosion. In our last issue we had a notice of the explosion of a cylinder at Polmadie. From inquiries, it appears that the bursting was caused not by the cylinder being overcharged, but by the admixture of hydrogen and oxygen in a compressed state. The cylinder alluded to had, it appears, been tested only a few months previous to a pressure equal to twice what would be required for an ordinary charge. During the time of the compression of oxygen, a considerable amount of heat is produced, but if a certain proportion of hydrogen be present, the amount of heat will be much greater. This heat upon reaching a certain pitch might be sufficient to cause ignition, and consequently an explosion, especially if coupled with concussion. From a letter on another page it will be seen: that it is intended in future to provide hydrogen cylinders with a left hand screw, which will prevent the wrong cylinder being attached to the compressing pump. Transparencies from Paper Prints without a Camera. Iv is a well-known fact that in a paper print there is much more detail than is visible when examined in the ordinary manner. Much of the detail is sunk in the paper, and when of a delicate nature it becomes united and presents the appearance of a uniform shadow. If an unmounted print is viewed by transmitted light, it will be found that many of the shadows contain delicate details which were not seen when the print was viewed by reflected light. If prints are copied by the camera, the finer detail of the picture will not be reproduced ; but, by another method to be described, lantern slides may be made from prints which will present more detail than shown in the original when examined in the usual way. Procure an ordinary printing frame, into which is affixed a piece of clear glass, and in the dark room place upon it, face up, the print to be copied. Then with that of the print. This is then secured in contact and exposed for a few seconds in front of an ordinary gas or lamp flame. On development it will be found , and others. upon this is placed a sensitized plate, its face in contact that upon the negative the most minute detail that was seen in the print by transmitted light will have been reproduced. From the negative thus obtained, a transparency may, by the same method of contact printing, be produced, which, when enlarged by the lantern, and compared with the original print from which it was taken, is seen to possess an immense amount of detail not observed in the original print. When a print has to be taken off its mount for the purpose of being thus copied, it is necessary that the greatest care be taken that the paper is not split or damaged, and that all the mountant be thoroughly removed, as any marks or imperfections upon the back of the print are reproduced. To remove the print from its mount, place it ina flat dish of warm water, which in a short time will permeate the print and soften the mountant. This is accomplished when, if a knife be inserted under one of the corners, the print can be peeled off. Some mountants will, however, become softened in cold water. After the print is removed from the support it is laid face down on a sheet of glass, and the back sponged to remove all traces of the mountant. The print, after being dried, may then be used in the manner above indicated for contact printing. The sharpness and quality of transparencies produced in this way are so great that it is impossible to distinguish the source from which they were taken ; particularly is it so in the case of portraits. From the foregoing it will be seen that those who possess portraits of friends, views, or other photographs, will be enabled to reproduce them as lantern slides without much trouble, and without a camera. 20! CAMERA Club Notices.—March 3rd, 8.30 p.m.. Smoking Concert ; 6th, § p-m., Mr. Andrew Pringle, on “ The Optical Lantern ;” 13th, 8 p.m., Lantern evening ; 17th, 8.30 p.m., Evening for Testing Lenses; 19th, 8.30 p.m., Smoking Concert, Annual Exhibition of Photographs ; 20th, 2 p.m., at Society of Arts, Conference and Exhibition of Apparatus, papers till 5.30 p.m.; 2mst, 10 a.m., ditto; at 7.30 p.m., ‘Annual Dinner at Frascati Restaurant, Oxford-street ; 27th, 8 p.m., Mr. Willis on * Platinotype Possibilities.” Tue conference in connection with the Camera Club will take place at the Society of Arts on Thursday and Friday, March 20 and 21, under the presidency of Capt. Abney. Amongst the papers to be read and discussed will be’ the following :—* The Art of Drawing and Photography,”’ by Mr. A. M. Rossi; ‘“ Photography by the Light of the Electric Spark,” by Lord Rayleigh ; ‘The Latent Image,”’ by Mr. C. H. Bothamley ; “ Limitations in the Treatment of Subjects by Focus,’* by Mr. T. R. Dallmeyer ; “ Collotype and Photoetching,” with practical illustrations, by Mr. W. T. Wilkinson; and other papers by the President, Mr. Lyonel Clark, It is further proposed to bring forward in as complete a manner as possible the subject of photographic exhibitions and their regulations. The exhibition ofapparatus will be as usual in the library of the Society of Arts. All photographers or others interested in the subjects under discussion are invited to be present.