The Optical Magic Lantern Journal (April 1891)

104 The Optical Magic Lantern Journal and Photographic Enlarger. sive quantity and quality had been arrived at, and the light allowed to be drawn back—the accident occurred. _But a far higher class than these have taken quite kindly to the use of the lantern for illustrating their scientific lectures. The Astronomer Royal for Scotland (Professor Copeland), the successor of the genial C. Piazzi Smyth, has;-like the latter, adopted the use of photography and the enlarging lantern in showing such phenomena as the spectra of the temporary stars, thus deducing ‘their composition from their photographed rays, as well as the rates of travel of many of them. The artists, too, who make no difficulty of sneering at the mechanical art, have no compunction through their representative in using the same instrument and means to illustrate the means by which art was fostered in the dark ages in the monastries and nunneries by the designing, painting, and beautifying the manuScripts, of which we have so many examples, and other works of that nature, done for the love of the subjects, not for the payment received for it. 1 am afraid that it will be a long time ere even the newest of the new theories and experiments in the Production of photography in colours by Mr. Ives in America, and Mr. Lipmann in France, will be able to help us to have our slides in the true colours of Nature. It would seem that with all the multiplication of words, there has been nothing more done than what: we already know, and have even shown by the aid of the lantern and the electric light long ago. In. the otherwise very enjoyable exhibition, at the first popular meeting of the season of the Edinburgh Photographic Society, by Mr. Gambier Bolton of his wild animals, there was one of a very Music Hally type which would be better left out in future exhibitions ; it was the first, and a portrait of the lecturer. with the honours, “ F.Z.S.,” &c., all around him. He had much better not be classed among the animals. 50% Ether Saturators. By A. W. ScortrT. THE past few months have.been trying to users of saturators, owing to the temperature being below its usual winter level. Persons who in previous seasons had used ether successfully have been troubled with pops and small explosions of gas in the tubes connecting the saturator to the jet. These pops, though quite harmless, are very startling when they occur unexpectedly. The reason is simple. The warmer the saturator the more highly saturated with vapour is the oxygen passing through, and the more highly saturated the oxygen is, the less explosive, and therefore the less liable to pops, it becomes. There are two forms of saturators at present in use — one is the double-barrel form, invented by Mr. Ives ; the other is Scott’s Warm-Air Saturator. If charged with the same fluid, and if both are used cold, there is no difference in the saturating powers of the two forms ; but when the warm-air pattern is heated, the saturating power is considerably increased, and this power enables cheaper grades of ether and also benzoline to be employed. The warm saturator is quite safe from pops, when fairly heated and charged with ether ; but if charged with benzoline it requires. more care, the gas being less highly saturated. Ives’ saturator is capable of 500 candlepower limelight, quite steady and noiseless; if charged with ether at about two shillings the pound, and used with a small-bore jet, it will rarely give pops, unless the weather is frosty, and even then an expert manipulator can easily avoid them. Pops are due to two causes—an improper jet, or too low a pressure of gas. The jet usually requires adapting to give the best results with ether, and this should be done by the dealer who supplies the saturator. The low pressure of gas is, however, the chief cause of pops, which occur when the light is being put out. In the case of a coal-gas limelight the practice is to turn off the oxygen tap of jet first, then to turn off the coal-gas tap. Now with ether the opposite course should be invariably pursued ; the vapour tap should be turned off first. This alone puts out the light, without checking the flow of gas, for the pure oxygen is still lowing on to the lime, and when the lime is: cold the oxygen can be safely turned off at the cylinder or gas-bag. ; When a pop occurs sometimes a few drops of ether are forced by the shock into the tube leading from saturator to cylinder. Hence this tube should be not less than 5ft. in length, to protect the regulator or gasbag from the ingress of these drops of fluid. 20: On “Pressure’s’”’ Riddle and Regulators in General. By HoRACE HILTON. Tus riddle (page 98) is easily explained by the fact that all regulators leak slightly, and I do not think that one could be made that did not leak a little after it has been in use some time. I will illustrate my remarks by referring to my own regulator. It is one of the ordinary bellows regulators(3in. x 3in. x 2in. wedge), and it leaks away its contents--if charged—in ten minutes. This bellows when. expanded has a normal capacity of the 13: part of a cubic foot, so that it would take 1,920 minutes (32 hours) to leak away a cubic foot. Now if my regulator were attached to a cylinder with an intermediate gauge affixed ; and if valve was turned and left on, no appreciable change could possibly take place in the gauge in the balf-hour mentioned by “ Pressure,” because in that time my regulator would have only leaked away three times its contents, or the <i part of a foot, and I do not think any gauge would show such a fractional loss. But directly the cylinder valve is turned off the loss at once becomes manifest in the intermediate gauge. because the regulator begins to lose its contents, and in consequence the gauge loses its pressure, the gas by back pressure passing off through the closing regulator. The foregoing calculation, of course, is on the supposition that all connections are gas tight (except where the regulator leaks). With reference to these regulator leaks, I was fora long time puzzled to know the cause, for I was certain that the bellows themselves were gas tight (and pres | sure proof), and till very recently had thought it a