The Optical Magic Lantern Journal (April 1893)

72 ternists are not millionaires. and the saving of 1s. 6d. or 2s. per exhibition is often « cousideration. here is a rough and ready Lut useful test for the quality of oxygen yas, aul that is, by the noise produced in its combustion. f£ keep one particular jet for the purpose. Usiny regulators on the cylinder, the cocks of this jet wre turned fully on, it the gas is good there is no noise whatever ; if slight vy impure, the cocks must be turned off a little to get a quiet livht, and with the worst samples of gas they must be nearly closed to secure quietness, and the light suffers proportionately. In these experiments the same regulators are used, and the bellows are fully intlated before the cocks are opened. Those who constantly use oxygen gas know at once whether the quality is yoo:l. bad. or indifferent ; but the ordinary amateur must depend toa vreat extent on the dealer, and not try to purchase too cheaply, as it has been whispered that some dealers (wll men have enemies and jealous rivals) keep a!) three qualities in stock and supply that which will best suit their customer's purpose, I mean his price. Mr. Spawforth’s argument in favour of the safety of using a mixed jet with hydrogen direct from the main would be tiauswerable if his premises were correct, but he forgets, or perhaps does not know, that the gas-main pressu.c is eyual to a coluinn of water from 1Jin. to2in. only, whereas the pressure from «a regulator is never less than 12in. and is more often 20in. or 30in.; and again, a cylinder has no outlet except in the direction of the jet. On the contrary, the gas-mains have thousands of outlets with a light at each, not to mention the comparability of such a lurge volume of vas as there must be in the mains. To illustrate what is meant, let him blow down the ucarest gas bracket when other burners in the house are alight and see whit will happen. I know it isa practice with some operators to supply the mixed jet direct from the main, but have these persons ever heard of the explosion which tore up the pavement of several streets near Tottenham Court Road some twelve years’ azo, which was caused by the mixture of common air in the gas-mains? How much more likely is an explosion to occur when oxygen gets into the main instead of conunon air.—Yours truly, C, GOODWIN NORTON, 35, Manchester Strect, W.C. —0:—_ Notes and Queries. Shade asks if Mr. Stevenson has any patent for the reflector in place of door of lantern on page 53, as he would like to adopt it, for healways lectures and operates himself at the same time. Mr. Stevenson gave the information for the use of anyone who cared to adopt it. dAmateu.—In last journal you gay you use the Lawson Saturator; would you please say (1) what you saturate it with ; and (2) if you consider it quite safe? Ansiwern.— (1) We use benzoline; (2) we have used it under all conditions, and as regards the identical one which we have, must say it is perfectly safe. J.G. Lhompson.—We cannot supply name and address of writer, it would be a breach of trust. Aurora Optical Manufacturing Co. (Lopeka).—The mikers of the apparatus you mentionare The M‘Intosh Optical Co., Wabash Avenue, Chicago. Ww. If, If. writes: Will you give me a list of the most useful photo apparatus for making lantern slides, and the cost of same. Iam a beginner, and have no apparatus? = dAnswer.—You will find particulars in “ Slide Making,” by A. R. Dresser. It was published by the now extinct Fry Manufacturing Co., but most dealers have copies. Price td. The Optical Magic Lantern Journal and Photographic Enlarger. J. Clijton.—We received your letter with photograph of saturator, aud wrote you to address given, but the letter was returned marked, insufficiently addressed. Please send full address. Lahibitor.—Messrs. Riley Bros., of Bradford, can supply you with: coloured window show-bills on which you can print particulars of your entertainment. Devon writes: I have w pair of gas-bags that I bought from a local dealer who has left the country. ‘They are nearly new, but they leak s» badly that they are no use. How can I repair them? Answer.—If the leak is at any of the seams, open it a little more. apply some Indiarubber cement and close ayain ; if the leak is in the body fasten a patch of waterproof on with the cement. J.J. Bontwood.—We know of no maker except Mr. Pumphrey, of Birmingham, who sends out books of paper prints of slides. John Wuswell writes: About two years ago I bought front Messrs. Riley Bros., Bradford, one of their ““supurb bi-cnial lanterns’’ (£12), with blow-through jet and Gin. focus lens. Some ten months ago I got telescopic tubes fitted, and exchanyed my Gin. lenses fur 10in.; while I had the Gin. lenses the lantern gave every satisfaction, but since I changed them for longer focus I cannot get all the picture in focus, 1f one part is in focus other parts are not. Can you tell me where the fault is and what are my remedies? «Answer—Your lenses evidently do not give a flat field. See article in this journal for October, 1892, page 12. Jon writes: J have madea shelf in my lantern box to run 1n vrooyves, and underneath have fixed a sheet of tin, to which is screwed a piece of shcet iron bent to the shape and size of a fire brick. On the top of the shelf my saturator is laid, with two holes at end of box to tix tubing on nozzles of saturator. The fire brick is heated and placed in the sheet iron receptacle to warm the saturator, but I should be glad if you would in‘orm me if there is any danger of the heat causing the ether to expand sufficiently to burst the saturator. If thereis nodanger I think the heated brick preferable to hot water. Ansirer,—No fear of this need be entertained. India asks: 1. Willa Dallmeyer No. 1 B. c.d.v. lens do well for an optical lantern with 4 inch double coudenser and the etho-oxyyen light, or would a cabinet (3 B) by same maker be better, I want a disc of about 20 feet? 2. What arc the dimensions of a Lawson saturator, and is there a means of opening it for recharging with absorbent material when required? 3. Is it necessary to pack a jet with pumice powder ? 4+. Which is best to employ for a saturator, benzoline, cther or gasoline? 5. If I employ two saturators of the kind mentioned will it be well to use one oxygen bag with a T piece? Answer.—l. Either lens will answer, for 20 feet disc it all depends on the distance you can get from the lantern, No. 1 Bis 6 inches focus, so distance from lantern to screen must be 40 feet, No. 3 DB is 10} inches focus and requires a distance of 70 feet. 2. About 4 inches on the base and 73 higti, not including the jet and inlet tube. No trouble about repacking need be anticipated. 3. No. 4. We employ benzoline by preference. 5. The second jet is brauched from the first (see S in sketch in this issue), or the plan you suggest will answer. H.H.if. 1. A greater angle of light is collected. You will find the subject of triple condensers fully treated in Taylor’s Optics of Photography. udvertised on the last page of this journal. 2. We had hoped to describe an excellent jet on a new principle in this issue, but could not get the illustration in time; it will appear in next. We hope to act on your suggestion. Radjah.—Coat the glass with varnish, and when nearly dry press printed matter in contact, and when dry rub the paper away with a damp cloth and finger. The result however will not produce w high class slide.