The Optical Magic Lantern Journal (August 1891)

140 The Optical Magic Lantern Journal and Photographic Enlarger. bers a few hints on the ‘ Method of Finishing the Negative.” He had found that amateurs took a great cleal more trouble in developing their negatives than professionals, but in fixing and washing they reduced the careful developing to xéJ. While the print was in the fixing bath they would look at it every now and again and admire; the air acting upon the silver caused the film to turn a sickly yellow. and the result was flat negatives. Speaking of the final washing. he said a negative not thoroughly washed was very liable to damp, to say nothing of fading and other kindred evils. He finished his excellent hints by some remarks on reducing and intensifying. An interesting discussion followed, chiefly on reducing and packing of exposed plates on a tour. PHOTO SocrETY OF GREAT BriTaAIN.—The rooms of this Society, (50, Great Russell-street, W.C.), were closed on the 2gth ult., and will be re-opened on the 2Sth inst. SHEFFIELD PHoTo SocieTy.—On July 7, Mr. B. J. Taylor in the chair, Mr. Hibbert brought for inspection G. Houghton and Son's Automatic hand camera, fitted with one of Wray’s lenses. Mr. E. Beck gave a practical demonstration on platinotype printing, by the hot bath process, which ‘was a great success, and fully appreciated by the members. CROYDON MIcROSCOPICAL AND NATURAL History ‘CLuB.— Photographic Section.— An ordinary meeting was held on July 3, when a numerous assortment of negatives and prints were exhibited, taken by members during the recent excursions, The next ordinary meeting on August 7. 10: Correspondence. EXHIBITION AT PALL MALL. [ Lo the Editor] Str,—The Exhibition Committee of the Photographic Society of Great Britain desire me to inform you that the annual exhibition of that Society will be held at the Gallery of the Royal Society of Painters in Water Colours, a, Pall Mall East, irom Monday, the 28th of September, until ‘Thursday, the 12th of November next. The exhibition will be opened daily (Sundays excepted) from ten a.m. to five p.m., and on Monday, Wednesday, Thursday, and Saturday evenings from seven p.m. to ten. The following gentlemen have been appointed judges, and thave consented to act: Messrs. J. E. Austin, F. Hollyer, P. H. Newman, F. M. Sutcliffe, and J. B. B. Wellington. Medals will be placed at their disposal for artistic, ‘scientific, and technical excellence of photographs, for lantern transparencies, and for apparatus, Negatives and transparencies, photo-mechanical prints, photographs of purely scientific interest, photographs coloured by scientific or mechanical means, and apparatus and appliances containing points of special interest. will be admitted ; but photographs coloured by hand will not be admitted. ; Photographic lantern slides will be shown on the evenings the exhibition is open, by means of the society's optical lantern, The Exhibition Committee will be glad to receive slides for exhibition, especially such as are illustrative of life and scenery in the British Colonies and Possessions. No charge will be made for exhibiting such slides, which should be delivered at the offices of the saciety early in September, dn order to enable thecommittee to group and arrange them. Slides, however, will not be eligible for a medal unless the conditions in the prospectus be observed. Blank entry forms and any further information respecting the exhibition, apparatus and lantern slides can be obtained on application to the Assistant Secretary, P.S.G.B., 50, Great Russell-street, London, W.C.—I have the pleasure to be; your obedient servant, H. A. LAWRANCE, Assistant Secretary. Photographic Society of Great Britain, 50, Great Russell street, W.C., July 3, 1891. Notes and Queries. Fred. A, Robinson writes : “Ihave a 3in. optical lantern, but am neither satisfied with the brilliancy nor size of the disc. Can you tell me if there is any other form of light that I can adopt without much more trouble or expense? It seems to me that oxy-hydrogen limelight is too expensive and troublesome for occasional exhibitions to a few friends in one’s private house. Is there any other means of getting the desired result? Ansover.—Doubtlessthe oxy-calcium or spirit jet would suit your requirements. You will find particulars of it in our issue for September, 1889. J. Knight, jun. —Fix your star dissolver as follows : Secure it in place with the small bye-pass tubes standing vertical, so that the bye-pass taps are on the upper half. Connect the hydrogen supply with the horizontal tube from the left-hand side of star, then the two tubes standing at an angle of 45deg. on the left respectively to the hydrogen tube of jets in upper and lower lanterns. The oxygen supply is connected in similar manner with the horizontal tube, at right-hand, and the other tubes with oxygen side of jets in upper and lower lanterns. After you light up, adjust the bye-passes ; a few minutes will suffice to enable you to understand the mamner in which either or both lights may be turned up. Rt. W. Stiles.—You do not state the focus of lens with which you want to makea 15ft. disc. If it is a gin. focus, the distance between lantern and sereen must be 20ft 3 if Sin., 25ft.; if in., 3oft.; if 7in., 35{t.; if Sin., 40ft.; and so on,” See the table in our issue fur last October. Murgen,—Look for a leak of light in the camera. L. Park,—The varnish pot may be new in this country, but it has been in use in America for the last ten years. M.—AIl lenses of the same focus will project a disc of © similar size at the same distance. The make or form of lens has nothing to do with this. LI. Davidson.—See reply to R. W. Stiles. The same rule applies, no matter what the distance may be; now in your case you want a r2ft. disc, with lantern 75ft. from screen. A lens of 18in. or tgin. focus. Ed. Beach.—In some back numbers of the Journal you speak of tubes being filled with powdered pumice. Kindly tell me what this is. Reply.—Pumice is hardened lava thrown out by volcanoes, Cautious.—Yes, the quantity of gas can be obtained by weighing the cylinder. Messrs. J. H. Steward, Strand, introduced a special kind of scales for this purpose. : B. E.—We cannot at the present give a list of the novelties to be introduced, but may perhaps in our next issue. Novice, B. B.,and EF, Hunter, —Queries came too late for insertion in this number. A POST-OFFICE ORDER has been received from Belgium, but without any letter of instruction. 705 EXPLOSION IN AFRICA.—We are informed by a correspondent in Africa of the following : It having been announced that the Rev. A. Vine Hall, of Claremont, would deliver an interesting lecture at Cape Town, on 23rd June, illustrated by the latest limelight views, an audience of between forty or fifty were assembled, when, at twenty minutes to eight, a loud explosion was heard. The explosion extinguished the gas in the hall, and caused. considerable alarm, but fortunately no panic occurred, The explosion took place, it is conjectured, by the accidental contact of the oxygen and hydrogen gases, which shattered the limelight apparatus, destroyed all the slides, and scattered the occupants of the room in all direc. tions. The explosion brought down most of the ceiling boards, and blew out some panes: of glass. Firemen were promptly on the spot, but their services were not required. The damage is estimated at 450. It is needless to say that the lecture did not take place, but will be reserved for some more favourable opportunity. ‘