The Optical Magic Lantern Journal (August 1893)

The Optical Magic Lantern Journal and Photographic Enlarger. oil in the lamp of each attains after an hour's work ; curious differences might be found, and when traced out to their causes, the information “would be practically useful. The conical shades to throw down the light from ordinary parlour oil lamps have been known, according to experiments tried by Mr. Ivison Macadam, to sometines raise the temperature of the oil in the reservoir to 86° F. A mistake, and an exceedingly common one, is the supposition that oils of bigh flashing point are under all conditions more safe than oils of the lowest flashing point authorised by Act of Parliament. A petroleum explosion is of the same nature as a gas explosion, that is to say, that there must first be a mixture of the particular hydrocarbon with common air. One result is, that when a lamp reservoir begins to get empty, an oil of low flashing point may be giving off enough vapour to keep air out of the upper part of the reservoir, and the vapour not then being nixed with air, an explosion cannot take place on the application of a flame. With a better oil, volatilising more slowly, there is more danger of an explosive mixture forming and being fired when there is free communication between the lamp and the reservoir. Mr. Boverton Redwood has publicly stated that for some years he and Sir Frederick Abel had examined the fragments of various lamps with which accidents had occurred in the metropolitan district, and wherever possible they had also examined specimens of the oil which had been used, and, later still, by desire of Colonel Majendie, they had made farther investigations into lamp accidents. The outcome was that some of the most violent explosions had becn found to have occurred with oils of high flashing point, so such oils do not under all conditions tend to safety. Most of the accidents in burning petroleum are due to defective lamps, and one made of glass or other brittle material should never be used, because of the liability to breakage. The proper construction of the lamp, and the keeping of its air-channels and other parts clean, are the chief elements demanding attention in minimising danger. What has been said, shows how many little points will require consideration in the construction of the best oil lantern of the future for optical projection, an instrument which is certain to appear in duc course because of the influence of trade competition, and because the advent of triple condensers of colourless glass at one great bound enables oil magic lanterns to be constructed for common use, and to yield a vastly better illuminated disc than average lanterns give at present. If behind such a : before being issued is simple condenser a Trinity House three-wicked Douglass burner be placed, and used with the samc oil as supplicd to lighthouses, whereby a flame of 180 candle-power will be obtained, these two elements alone will give an oil illumination of the screen not commonly seen. Unless my memory is not at fault with lapse of time, Sir James Douglass told me some years ago that he had given up all his patent interests in the paraffin burners known by his name, and that anyone is at liberty to make them; but before anyone does so, he had better make sure that L ain not mistaken upon this point. This threering burner requires an abnormally long chimney, which is not necessary with the two-ring burner; the latter gives the light of sixty standard candles. —0.—— Cylinder Notes. By A, M. Hippon. Some recent experiences lead me to believe that, as often as not, it is the mismanagement of the cylinder of comnpressed gas which causes those trifling mishaps and hitches which occur to the beginner when he first operates with some form of lime-light. Some novices at first regard a full cylinder with an undeserved amount cf apprehension and distrust ; and then afterwards familiarity breeds a contempt which resu!ts in the cylinder receiving a more careless treatment than it should be subjected to. Perhaps a few odd notes and wrinkles, none of them new, may be of use to those who during the next scason intend to operate with compressed gas for the first time. A visitor leaves an oxygen factory with two impressions firmly fixed on his mind :— Ist, a fecling of wonder at the complicated automatic machinery by which the gas is produced ; 2nd, the thorougliness of the precautions and safeguards which are to eliminate the slightcst possibility of an accident occurring to the user of the cylinder. The method by which oxygen is extracted from the air is not to be explained by the unmechanical mind, suffice it to say that the process is very elaborate and perfect, and that the pure oxygen is rapidly evolved to an accompaniment of rather weird and aweinspiring whizzes, clashes, bangs and snorts. The gas is stowed in holders and from thence is pumped into the cylinders ; four of them being filled ata time. A safety valve on the pump renders it impossible to compress more tban the proper quantity of gas into a cylinder. The contrivance by which cylinders are tested but perfect.