The Optical Magic Lantern Journal (July 1892)

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The Optical Magio Lantern Journal and Photographio Enlarger. 81 success of the slide; and if you have an idea that you can leave your outline undecided, and then ‘knock it into shape’’ when you come to the colour, you may be quite sure that when your picture appears on the screen, it will look quite different from what you expect, and will be dirty, dull, and confused. But a well-painted picture, with all its tints properly graduated, so that it is really brilliant, and not crude and garish in colour, will look brighter on the screen when shown with an ordinary blow-through jet, than a photograph shown with a mixed-gas jet, or even ethoxo-lime-light. 202 Jottings on Lantern Manipulation. By G. R. Baker. WirTH a subject like the manipulation of the optical lantern, one is somewhat at a loss to know what to include and what to leave out when treating the matter technically, for some elementary matters must of necessity be touched upon. I shall, however, try to give the results of my own experience, rather than a complete resume of what can be accomplished by the optical lantern, for the lantern world have already had lectures, papers, and demonstrations by such well-known menas Messrs. A. Pringle, Nelson, Traill Taylor, &c., besides which, many books are accessible to lantern workers, and last, but not least, we have Lhe Optical Magic Lantern Fournal each month, which will show students and others the scientific and educational uses to which projection apparatus can be put. The first necessity is a good and powerful light, and although fair, if not very good, results can be obtained from mineral oil lamps, with three and four wicks, I venture to predict that for all public work, or even for home use on a small scale, they will be entirely superseded by the electric and lime-light before many years have passed. This is distinctly an age of progress, and the great aim of everybody is to get efficiency at a saving of labour. The introduction of compressed gas in cylinders, at a very small cost, has almost entirely stopped the manufacture of oxygen for private use; and in like manner, the general adoption of electricity will, in a few years, “give us means, by simply turning on a switch, of having a light for our lantern or any other projection that may be required. The heat, bad smells, and general discomfort of working with a powerful paraffin lamp is intensified after a long interval of working with the lime-light, when for some purpose one has to resort to it, and perhaps I shall be best employed by endeavouring to dispel a few of the doubts and FALLACIES CONNECTED WITH THE LIME-LIGHT, AND ITs Sarge UsE IN PuBLIC oR PRIVATE, AND ALSO GiIvE Some Hints RESPECTING APPARATUS. 1st. As regards danger, Oxygen cannot explode by itself. 2nd. If a constant pressure is kept up, no one need fear to use the two gases under pressure in separate cylinders, with the same confidence if not more, than with the blow-through jet and one gas (oxygen) in a bag. ; 3rd. The jet must not have too large an orifice in the nipple for the pressure used. ; 4th. With a Fleming’s Safety Explosive Gas Tester the operator may always know if he has pure gas or not. —— sth. A cut-off arrangement prevents interference with taps, after once adjusted for best light. ws The modified method of using the gauge so that contents of cylinder may be known without submitting such gauge to undue strain. 7th. Fixing of tubes. As regards oxygen, what risk do users of compressed oxygen gas run? If the companies test the cylinder to twice the pressure of gas pumped into same, then if there is no deterioration of the cylinder and care is taken of it in transit, there should be no element of danger here. Owing, however, to the apparent strength of these cylinders, users and carriers of them had already began to treat them contemptuously, when one or two incidents occurred that acted as cautions, and showed how necessary it is to take care of anything that is useful. Is it taking care of a cylinder when filled with gas, and fitted with a comparatively delicate part known as the valve, to pitch it about as if it were a piece of timber or bale of wool, or violently stand it down on its valve end? No; and when, as happened some little time since an injury resulted to the valve and the gas escaped with sufficient violence to clear a railway station platform—it shows that on no account should a finished cylinder after testing. either with or without gas in—be sent by rail or carrier otherwise than in a box or protecting crate; for it must be borne in mind that the strength of a vessel is represented by its weakest part, and that in this case is the valve. Other small accidents have happened to cylinders. damaged in transit, but in no case have I had any difficulty, or know exhibitors to have diffculty when the cylinders have been taken care of. The leather portmanteaus for pair, or the: