The Optical Magic Lantern Journal (May 1890)

92 The Optical Magio Lantern Journal and Photographic Enlarger. The“ Giah” is made in two sizes—the lantern plate and quarter plate. The rapidity with which it may be worked offers opportunities for placing on record many momentary scenes of street and country life, which it would be difficult to obtain by any other means. Fig. 2 gives a representation of this most acceptable novelty. We have to congratulate Messrs. Mawson and Swan upon being able to produce such an efficient apparatus, and we hope at no distant date to hear that they have decided to make a stereoscopic camera on the same principle. s02 A Simple Support for Lantern Fronts. WE have had suggested the following simple method of Raining stability for the fronts of lanterns. Around each nozzle is attached a collar, fastened in the same way as that used on small telescope stands. From this collar, both top and bottom is attached a rod of a few inches in length. On one is cut a screw thread, and to the end of the other is attached a Capstan swivel, with a thread at the end to fit the Screw upon the rod. To operate, the swivel hanging from the lowest nozzle is screwed on to a rod fastened in an upright position on the lantern stand ; the swivel pending from the middle nozzle is then secured to the Projecting rod of the lowest nozzle, and in like manner the top and middle rods are fastened. By tightening the swivels, both support and stability are imparted to the nozzles. 10: New Method of Preparing Engravings for the Lantern. THERE are innumerable engravings to be found everywhere, and especially in the illustrated monthlies, that are so well adapted for converting into lantern slides that the wonder to meis, that they have not been utilized for this purpose long since, or that attention has not been more specially called to their fitness for such use being made of them. Having a series made for my own use from a source such as that mentioned, and having shown them to discriminating spectators with the most excellent effect, I am of the opinion that a few words on this subject will be of use to my fellow-readers of this journal. I do not think that there is the slightest necessity for trying to pass off photographs of engravings for photographs from nature, for it is quite a mistaken idea for any one to cherish that photographic subjects are alone fitted for even a high-class lantern entertainment. However, when the lines in the engraving to be copied are ofa too obtrusive nature, it may be advisable to tone them down. This may be done in two ways, both of which I shall mention. The first of these is to photograph the engraving in such a way as to break up the lines in some measure. The best system I have tried is to cover the engraving with a thin and rather finely ground glass, keeping the polished side of the glass down, the ground side being uppermost for a reason I will just give. It is of paramount importance that the glass be scrupulously clean and that no greasiness be present on the ground surface. An application of ammonia (followed by water), nitric acid, or even soapsuds will ensure this necessary condition. Now, having laid this plate down upon the engraving in the way I have prescribed, note that everything has now a pencilled effect, that the bold blackness of the engraving has given place to precisely the appearance as if the work had been executed by a graphite pencil. None of the lines are now visible as lines, but a delicate softness pervades every part. If a photograph were taken of the print in this state it would be too soft to be of much use. But to impart all the original vigour to the salient portions of the picture, it is only requisite that a brush charged with oil be passed over the ground glass. when it will acquire its pristine blackness. As the weakest parts of many engravings are the skies and foregrounds—by “weakest” I mean here those parts in which the lines show with most marked prominence—such portions should not be oiled, or if so it should be very sparingly done. A calico rag is useful at this stage, as by rubbing with it, any part may have its strength subdued to any necessary or desired extent. When a negative is taken of either a wood or steel engraving that has been “faked” in the way described, anda transparency then made from such negative in the usual way, it is exceedingly difficult to discover when on the screen that the original may have been an ordinary wood-cut in the Century or in any of the illustrated papers. The second way to which I have alluded, consists of photographing the engravings in the usual manner, but putting it a little out of focus when doing so. I have never found this quite satisfactory. Neither has it been satisfactory to have the transparencies quite sharp, and then put them a little out of focus when throwing them on the screen. If a transparency of this kind must be shown, it is much better to havea special old-fashioned un-achromatic lens in the lantern, as it does not give absolute sharpness, no matter how carefully the attempt to focus is made. This is the better plan of the two, but still it is not eminently satisfactory, for owing to the general use of achromatic lenses in lanterns, the public are now educated to expect the acme of sharpness in projected Pictures ; and they will not easily be satisfied with less. Having now described the two ways by which engravings may be prepared for lantern exhibition, I say without any hesitation that the first system is so greatly superior to the second as to leave no room for comparison between them. The adoption of this method of preparing engravings instead of natural Photographs for lantern work will Open up a wide door of usefulness in the preparation of illustrations for lectures on travel, and indeed on any of the thousand and one topics which are treated in illus. trated serials and books. W. BLoxuan, M.A. A Simple Apparatus for Generating Oxygen Gas. C. F. GOHRING recommends the below-described method and apparatus (says the Photographic Times), for preparing pure oxygen gas on a small scale.. A large flask with spout, and graduated, with a rubber stopper through which three stoppered funnels Pass.