The Optical Magic Lantern Journal (March 1901)

36 The Optical Magic Lantern Journal and Photographic Enlarger. 2152. 31st January, 1901. Ian Robertson. Improvements in the method of projecting coloured lights and for imperceptible changes from one coloured light to another for stage purposes and otherwise. 2456. Sth February, 1901. Henry William Hamblin Palmer. Improvements in mechanism employed in the production and reproduction of a series of photographic pictures. Copies of the following specifications may be obtained by remitting 1/for each specification to W. P. Thompson é Co., Patent Agents, 3822, High Holborn, London, W.C. SPECIFICATIONS PUBLISHED. 17 of 1900. Wallis and Wallis. Envelopes and holders for sensitive photographic plates. 1530 of 1900. Vickers and Rumsey. Apparatus for photo printing and developing. 16075 of 1900. Hagey. photographers. 17366 of 1900. Adt. Eye-glasses. . ’ 19547 of 1900. Goodson. Chimney raising appliances for lamps and stoves. 23 of 1900. Edmundson. Apparatus for the production of acetylene gas for street lamps, gate posts, carriage and ordinary illumi nation. SWE GLIA Ore J ‘| Bétes and Queries. 9° Correspondents must supply their names and addresses, but, if desired, queries can be replied to under a ‘‘ nom de plume.” Clement & Gilmer.—A few months ago we had a somewhat similar letter from the United States. Projection on the clouds is a rather tall order. Some clouds are much nearer the earth than others, and in striking an average distance it will be about 4,000 feet; but as the distance is never constant, I am afraid you will find it a hopeless task, However, taking matters at 4,000 feet, this distance can be experimented with by trying a projection on some building at such distance from the lantern. In order to ce a projection at this distance the disc would, we presume, require to be about 100 feet at least. With an ordinary sized slide a lens of about 10 feet focus would be required, but given the size of slide you intend using, the distance that the screen it to be away, and the size of disc required, the necessary focus of lens can be ascertained as follows:—Multiply the distance between lantern and screen by the size of the opening of tlide, and divide by the size of disc. Much of the light would pass through a cloud, and only a small percentage reflected ; consequently, with regard to the lignt, you cannot have it too powerful. J. S. McCulloch.—We thank you for the tickets for the Edinburgh Photographic Exhibition. H. Andrews writes :—With regard to the query in last issue by * Photophil,’’ he may be interested in the following quotation from page 304 of Mr. Lewis Wright's book on ‘Optical Projection” :—‘‘Ammoniated copper gives a fair blue, but a much better plan is that discovered by Mr. H. G. Madan, of superposing Chance’s signal green which stops all red on a rich cobalt-blue glass which | transmits little but redand blue. The two only transmit Exposure scales for use by ; | rays between the F and G. In all colour experiments it has to be remembered that deeper tints are needed in proportior to the brilliancy of the light used in the lantern. N. Pachcovsky.—(1) Write to Messrs. Newton & Co., 3, Fleet Street, London, E.C., for particulars of the micrcscopic attachment for lanterns. (2) There may or may not be lantern goods exhibited at the forthcoming Glasgow Exhibition, but it is certainly not intended solely for the exhibition of lantern goods as you seem to imagine. We will endeavour to supply the information about the lamp in next issue. R. I’. says:—I am only a beginner with the lantern co please excuse my question which to you, as an expert, may seem frivolous, but to me my trouble is vexatious. The trouble is that I can only get a small brightly illuminated circle of light with my lantern; the circle certainly continues to the required size but is somewhat dark beyond the bright patch alluded to. Can you suggest avything to overcome the difficulty? I have ; written to the makers, but they only say that the apparatus was right when they sent it off and that if I want them to look at it again I must return it and pay freight both way. Ans.—The remedy is a simple one. Place the light alittle nearer to the condenser. If matters are not amended thereby write ue again. Edgar Oates.—(1) We are afraid that if you introduce dissolving views and the cinematograph, using acetylene gas only, in conjunction with your conjuring entertainment, you will spoil the whole show. Acetylene is not powerful enough for your purpose. (2) The arrangement of a cinematograph projector attached to the lower lantern, and Beard's carrier at the top will answer. (3) It is quite possible to project the slides from the top lantern of the same size as the cinematographic pictures projected from the lower lantern. If you tell us the distance between the lantern and screen, and the size you want the picture to be, we can let you know what focus of lens to employ in the top lantern for projecting ordinary slides to occupy the same size on screen as your cinematograph pictures. (4) In our next. W., H. Young.—Thanks for book. In our next. W. Carter.—The light spoken of was never commercially introduced. The apparatus consisted of a species of pump, which increased the pressure of the house gas before it reached a small burner furnished with an incandescent mantle. # Correspondence. 3 LANTERN STANDS. To Mr. J. Hay Taylor, Editor. Sir,—Referring to your Journal last month as to rickety lantern stands (‘A Hint to Many Photographic Societies ’’), it is strange to me that no one has revived the very firm iron stand designed by Francis, of Museum Street, many years ago. I have had one for over 30 years. It is a most useful stand, firm and simple iu . construction. Atacost of about 25s. it could be mada by any iron founder. 5282 AS As a lantern stand in a hall or schoolroom it is perfect, no fear of its being upset, firm and rigid, no shaking being possible, takes up little space, and has every movement for adjustments, etc. Wallingford, Berke, Yours, etc., FRANK HOWARD.