The Optical Magic Lantern Journal (April 1891)

Tho Optical Magio Lantern Journal and Photographio Enlarger. 101 with a view to simplicity of parts, the frame portion Experience with Ethoxo: Limeof the shutter and the stop of the lens are formed of 3 mos ue same piece of metal, and it is on this that the Light. shutter slides. 2x The shutter, when set, is held in position bya small By ALFRED PUMPHREY. ~ hook clip, which also acts the part of a spring to retain the shutter onits return. After being released, the shutter flies upwards by the force of an elastic band, but no sooner has it done so than the band disengages itself, and another causes its immediate return. All this is done in the fraction of a second, and with great certainty. A pneumatic fitting can also be used with this form of shutter, which enables time as well as instantaneous exposures to be given. This camera (see cut), which resembles a} small | sample case, accompanied us during the Easter holidays, and we found it capable of doing excellent work. 0% Pressure Gauges, MEssrs. NEWTON & Co. in writing to a contemporary have furnished the 1ollowing valuable information for | ensuring safety with pressure gauges :— “There should be no cast-iron in the gauge : the tube and works should be mounted on a brass or gunmetal frame. The glass covering the dial should be mounted in a ring, fitting on the body of the gauage like a cap ; when the gauge is in use this cap should be removed, thus avoiding all danger from the broken pieces of glass. The gauge should then be inclosed in a brass wire cage, so that, should the tube burst, any portions ‘of metal. would be caught by the wire network, and, if not stopped altogether, would at any rate be rendered harmless, “ Our employes are constantly using gauges for testing gas bottles, and we have always had our gauges made in this way to avoid any risk from accident. The screw valve of the bottle should not be turned on full, one complete revolution of the screw is quite sufficient ; this greatly minimises the risk of fusion caused by friction, as the cylinder would probably take a quarter of an hour to empty itself. Of course the same gauge should never be used for both oxygen and hydrogen cylinders.” 20: A CLOUDY or rainy day permits the making of slides as good as those made witha strong light. It is only necessary to use a much larger stop, or a Jonger exposure, or both. — V. L. Davey. . I SHOULD like to reply to the letter of your correspondent, Mr. C.G.Norton. He thinks he has “ taken every known precaution ;” on the contrary, I think, from what he says, he has had little real experience of what writes about. The ethoxo light is quite safe in the hands of a competent man, who has suitable tools and has proved them ; a candle is a dangerous thing in the hands of an infant. First of all, your correspondent does not use a pair of tested flame extinguishers. 1 enclose particulars of how these are tested. With these, had the mixture become explosive from want of ordinary precaution, the explosion would not have been alarming in a crowded room. The cause of your correspondent’s explosion was that the oxygen did not take up enough of the ether, either owing to the vapouriser being too small, or from a reduction of temperature caused by the continued evaporation of the ether, or from the vapourizer being used in too cold an atmosphere. In using gas from a cylinder it should be borne in mind that as the gas expands it falls in temperature, exactly in the same way as it rose in temperature as it was compressed, and that a low temperature is unfavourable to the comelete saturation of the oxygen with the vapour of ether. It does not, therefore, follow that instructions which are adapted to the use of gas bags will answer equally well with gas from a cylinder, unless the operator uses his judgment and increases the temperature by some such plan as applying a little heat in the shape of a hot water bottle, or a hot brick, and enveloping the whole in a woollen cloth. I say that the ethoxo light is safe in competent hands, with suitable tools, by aman that has proved them. By that I mean one who has experience with his tools under different conditions. Because a light is all right when first started, it is not safe to conclude that it will be right after working for two hours ; it must be proved for the time it is expected to burn. The correspondent should never have come near the condition he describes—of the vapour giving light without the addition of pure oxygen. He speaks of precautions recommended by the sellers. I cannot, of ‘ course, say what others recommend ; but certainly he has not followed the precautions which I give in my little pamphlet, “‘ Lantern Manipulation.” There is one other point in which I think your correspondent does exactly the opposite to what I have found best. He says he “ made the adjustment at the jetand not at the cylinder.’ I find the proper way is to make the adjustment at the inlet of the vapouriser, so as to prevent any contamination of the supply of pure oxygen. I have always found this an important item. If the correspondent will give the measures of the apparatus he used, I should be able to say if the fault lay with the tools or the conditions. I shall be pleased to explain in next issue the conditions of safety as I have learned them from some years of trial.