The Optical Magic Lantern Journal (June 1896)

The Optical Magic Lantern Journal and Photographic Enlarger. use of an optical oil lantern, not to mention the smoke, smell, and great heat, are sufficient to make one hesitate before starting an enlargement in the dark room, or venturing into a drawing-room full of ladies. In both eases the final ‘‘blow-out ” is a relief to all concerned. Turning now to the use of the limelight, with its great brilliancy and immense power, there can be no doubt that to the vast majority of those I now particularly address it would prove a needless waste of energy. In the first place, for dark room work its heat is intense, it requires almost constant attention while at work, and the flame is after all not so steady as one would wish. Taken into the drawing-room, the hissing is objectionable to the audience, while the small innocent explosions which sometimes occur within the lamp are very unpleasant if it is doubted that the lamp is in careful hands. Possessed as I have been for the last six or seven years of one of these “‘ parafiin oil optical furnaces,” which I generally used in a very harmless way for micro projections, and throwing a six or seven feet disc comic slide on the screen now and again to amuse my children, I kept an open mind, as Mr. Gladstone used to put it, for any reasonable improvement short of increase in ‘‘ furnace’”’ power. Over a year ago I began to turn my attention to the Welsbach incandescent gas light, which was making electric light promoters feel rather uncomfortable in many quarters, and about the same time a writer in one of our journals ‘“ wondered whether this light would give a better colour than that of oil in the magic lantern.” Having procured from the Incandescent Gas Light Company one of their burners, I had it fitted to a stand to go into my lantern, and made so that the centre of the illuminant would coincide with the axis of my condensers. As some may not have studied the construction of the Incandescent Company’s lamp, I would like to describe it generally. It consists ofa Bunsen burner with its tube widened out at the top, into which is fitted a wire grating with a circular stop in the centre, which does the double duty of dispersing the flame equally round the burner and serving as a stand for supporting the porcelain stick, to the top of which the mantle is suspended. As the mantle forms the subject of patent, and not being a chemist, I can tell you little about its components, but I believe it to be constructed of material resembling the cotton from which ordinary wicks are made, and which is dipped into a liquid consisting mainly of thorium after being woven. From what I saw at a 105 kiosk at the Amsterdam Exhibition last summer, where a large working exhibit in mantle-making was going on, I can quite understand that the manufacture of these articles must be a very remunerative business, and possibly well deserving of the most jealous protection against competition. Although personally I have not the slightest interest in the Incandescent Gas Company's concern, I think it may interest the meeting to quote from the printed report by the manager of the Leith gas works, which states that for the cost of 1,000 feet of gas, viz., 33. 6d., the incandescent electric gives 1,540 c.-p.; common gas in a fivefeet per hour jet, 5,000 c.-p.; and gas in the incandescent Welsbach burner, 18,440. Returning to the subject-matter of my paper, viz., the adaptation of the Welsbach light for ordinary lantern work, I find in it all the superior convenience which gas _ always possesses over oil lighting—minimum of trouble, absence of smell, and almost complete safety. A few yards of rubber tube attachable to any convenient jet is the only requisite. The tap gives the power of instant regulation, and the lamp in the lantern may be left burning by | purpose or accident any length of time without attention or danger greater than that of neglecting to turn out the “lobby gas before retiring.”’ In connection I may here confide that although I seldom ‘hardly ever’’ forget to turn out a jet before locking up,I did so on one occasion with this lamp. I was admiring anew slide which I had that day purchased, when I was called from my dark room, and forgot to return. Next evening, on entering the room, my classic statuary figure burst forth in full view, to my atonishment, and knowing the joke only cost me about a penny, I think I can afford to tell you it in confidence, at my own | expense ! Considering this light from an optical point of view, I find its colour compared with an oil lamp a great improvement, resembling as it does that of the lime and electric are lights. A purity and crispness is at once discernible, and, what is much more valuable to us, its actinic power is very much greater than that of oil, and as we well know shortening of exposure in enlarging means prevention of fog, this attribute alone should be sufficient to commend it to your consideration. The lantern is provided with a circular hooded chimney to take the ordinary funnel of the lamp, and although I have found no serious tendency to breakage, I have adopted the mica chimney in preference to glass. This chimney costs only 1s. 4d,, and with care will last many