The Optical Magic Lantern Journal (June 1895)

108 The Optical Magic Lantern Journal and Photographic Enlarger. CONVENTION AT MONTREAL. To the Iditor. We hold our U.S. Photographic Convention in this city, commencing August 6th, 1895. Anything I can do for you at that time I shall be pleased to do. If any of your friends wish anything taken care of, or represented at said convention, my services can be obtained. Tam, yours fraternally, JEX BARDWELL, 98, Cass Street, Detroit, U.S.A. _—_0:—— Notes and Queries. J. Brown Scott writes:—I want to hit upon some method of showing on the screen by means of the lantern the ‘‘ Black drop" seen during the transit of Venus. Of course it is possible to devise a complicated rockwork slide to exhibit the effect ; and, as a matter of fact, one was made at considerable cost for the old Royal Polytechnic. Its mechanism has always been kept a secret ; but I have reasons for knowing that it is purely Mechanical. The problem is, tow can this be shown on the sheet to an audience? If possible, I want some contrivance which will enable it to be done as a part of an astronomical entertainment, and, therefore, with ordinary projection apparatus, I imagine, thatif it can be done at all, one lantern only will be used. If you can think of any dodge by which the effect can be shown, I shall feel extremely grateful to you for information. Ans.— We do not asa rule give sketches in this column, but will make this the exception.—Would something like sketch answer with single lantern. A, sun, B, glass slip with Venus G provided with two bearings UL, resting on c and D, F is position of glass slip when Venus is at x, 13, levers attached to K to represent the drawing in of the sun. With a bi-unial lantern the pear-shaped effect at the junction of drawing in of sun and venus could be more perfectly rendered. A. B. Spawforth—We find that a letter of yours of February 14th has got mixed with other papers, and the following query was not answered :—What actual loss of light is sustained by using 43 inch condensers (ordinary double plane convex) instead of 4 inch, for instance, if the light transmitted by the 4 inch is 100 °/,, what per centage would be lost by using a 44 inch one? Ans.— If the foci were about the same, there would be no difference. P. H. Grandon, Jersey — We have communicated with the steamship company, and learn that they will not carry cylinders, filled or empty,—You could use the form of gasometer for a triple if you made the tube of sufficient diameter to give the necessary pressure. If you want to cap the tube so as to get rid of the upper weight of water for moving purposes, you can screw a cap on the tube D (see sketch on page 58), and empty the top reservoir, and refill it when againusing it; but you cannot remove any of the water from the lower reservoir. Be sure that the tap A is closed. (2) We cannot give you the name and address of the writer of the article; but if you send us a stamped letter with his nom de plume we will forward it to him, and if he communicates with you, then well and good. G. H. Philp writes:—In your Journal for January, 1894, there is mention of a pair of lanterns with 24 inch condensers. Owing to the humorous, and halfchafting style of the article in question, I should like to know if itis meant to be taken seriously, and is it an absolute fact that a pair of lanterns with 24 inch condensers were once ordered and constructed. Ans.—The order for the large lanterns was given, and the whole thing is a fact, but although the lantern, &c., was duly completed, we understand that the condenser portion was never finished, although several castings were made, for they were somewhat imperfect. However, aftera great deal of money was spent upon it, the apparatus eventually found its way to the auction rooms of Messrs. Stevens. The further history cannot be traced with absolute certainty, but rumour says, the holes for the condensers were cut out to the base, and that they made excellent kennels for a couple of large Newfoundland dogs. A. H. Whilcher (Ottawa).—(1) It is well to trim off the extreme corners of the wicks, but from your sketch yours seem overdone. It is not necessary to trim them to this extent, notwithstanding the fact you received them thus from the maker in England. (2) Newton's transparent screen is made of fine cambric, and can be used dry before it has visited the wash tub, but once having been washed it is best to wet it each time of using. W. DM. D.—(1). If by separating the component parts of the back combination you do not obtain a flatter field with your short focus lens, you can do nothing more to it. (2). There is no necessity to empty out the oxygen, it will not harm the cylinder by being kept over till next season. (3). The mark (double B combined), is the mark of the Brin’s Company.—The (T & §.), intertwined ia that of the Projectile Company.—The number (6880), is that of the cylinder, but we do not know what the (3) underneath is for. The (xx.) with line between, is the annealing mark of Brin's, but as you have not drawn it as given by them, we suppose it must refer to another company, especially as the date 17. 5. 94. is six months later than the date at which this particular cylinder was tested by the Brin’s Company, From the particulars however, we cannot tell the maker's name. (4). Yes. A single achromatic lens will do for copying lantern slides in camera. W.J.C.—In the hands of an adept with either glass or films, there is practically no difference in the results. 10. WaLrTerR TYLER's ANNUAL Boatinc Trip.—Mr. Tyler, having invited his employés’ and friends to the number of over one hundred to participate in his annual outing, the large party after getting comfortably settled down in saloon carriages left Waterloo Station at 9.40 a.m. on the 24th ult., for Windsor where the steam launch ‘“ Her Majesty,” was, by previous arrangement, found to be in waiting to convey the guests to Henley. In accordance with an admirably arranged printed programme, the trip was broken at Marlow and other places en route. General good feeling prevailed throughout, and music formed one of the attractions when afloat. Soon after the time of starting it was evident that Mr. Tyler, as is his wont on such occasions had catered liberally for the ‘inner wants of man." It was generally voted that this years’ trip even surpassed that given by Mr. Tyler last year, and it goes without saying that everyone had a thoroughly enjoyable day. Waterloo was reached about 10 ‘p.m. when the party separated.