The Optical Magic Lantern Journal (January 1892)

4 The Optical Magio Lantern Journal and Photographio Enlarger. tive. The centre of this shutter was ground, and gradually vignetted into the clear glass portion, so that when passing in front of the lens no line of demarkation was to be seen upon the screen. The reason for the peculiar form of the upper part of the lever which directly actuates the carrier is to enable the pin of the second lever to disengage itself as soon as the slide is in place, and allow the continuance of its movement to gradually disclose the picture upon the screen. 20% Gas Bottles and their Safety.* By F, A. Bringer, THE use of gas in cylinders has now become so common that the public has ceased to regard it as fraught with any risk, and, considering the immense number of cylinders, now filled and emptied every week, the few accidentsthat have happened certainly justify the confidence hitherto reposed in their safety. As far as I am aware, no case has occurred of the bursting of a cylinder from over-pressure ; they are actually tested to double the strength they are supposed to have to withstand. Stories are told of 15 or even 17 feet of gas having been pressed into a oft. bottle ; but it has. never occurred to me—at least, if it has, the extra has never been charged for—so I am inclined to think it was notthere. Fullcylinders have been known to fall from an upper window on the stones below, without exploding; heavy weights have been dropped upon them from a great height with * Extract from Paper at London and Provincial Photographic As,ociatiun, out doing any further harm than spoiling their outward beauty, which, it must be confessed, is not very great. We may, therefore, say that so far as the cylinders themselves are concerned there is not much to fear, as except accidentally the ordinary user would never expose them to such tests as they are subjected to by those who make or fillthem. Only recently, at one of the principal railway stations, a large cylinder was let down suddenly on the nozzle. The result was a waste of eighty feet of oxygen and a general scene among the passengers on the platform. These accidents, however, might have been easily prevented by putting the cylinders in boxes during transit. What we really have to consider is the bursting of gas regulators and gauges, and our object is to find out, if possible, the cause of these accidents. First, then, the regulators. There are not many worthy of the name, the best, to my mind, being made by our friend, Mr. Beard. The principal fault with other makes I have seen tried is either that they don’t regulate, or if they do their action is so erratic as to make them unreliable. As to gauges, the simplest form is known as “Suiter’s patent.” Here you have no glass, and the worst that can happen is the blowing out the end of the tube, and waste of the gas. The well-known Bourdon gauge is much used, and very useful, because it can be kept attached to the cylinder, and it is easy by its means to see from time to time how the gas is guing. I need scarcely say it is not safe to use one of these for oxygen which has been used for any other gas. Not many days since an exhaustive inquiry was held to ascertain the cause of the bursting of both a gauge and a regulator, and this is really the reason the subject of “Gas Bottles and their Safety” was chosen for our consideration. I will tell you, as briefly as possible, exactly how it happened. Wishing to know whether a cylinder was full or empty, I relieved the gauge and reguletor from the one just exhausted, and firmly screwed it into, the cylinder, the contents of which I was anxious to ascertain. Turning the gas slowly on, the gauge immediately responded. I then turned the gas off again, and calling a friend, I repeated the operation of turning on the gas. The needle of the gauge rapidly registered 120, went past that number, and before I could turn the gas off again, the explusion occurred. I still held on to the cylinder and endeavoured to stop the waste of gas; the valve, however, would not act, and after inhaling more oxygen than was good for me in one dose, I came out of the dark room.