The Optical Magic Lantern Journal (May 1895)

The Optical Magic Lantern Journal and Photographic Enlarger. 85 are absolutely incombustible if unmixed. The probability is that one of two things would happen. Hither a mixture would take place at once in the jet chamber, which would explode and snap the light out, or a little hydrogen would burn at the jet, and the rest would pass into the oxygen bag, where, after some minutes, an explosive mixture would be formed, which would be fired from the light at the jet. The latter would probably happen if we were to work an oxygen bag quite flat and almost empty while the coal gas bag was about half full, as | Mr. Lewis Wright tells us was once his case. Retort explosions may be divided into three kinds, viz., explosions of the chemicals, owing to the introduction of carbonaceous matter; stearn explosions from leaving a retort to cool while coupled to the purifier, and the setting on fire of the retort and mixture through defective workmanship in the retort. guarded against by buying chemicals from a druggist of repute, and letting it be understood | what they are wantcd for; the second, the only result of which would be the blowing off of the tube, and the scattering of dirty water, may | be prevented by uncoupling in time; and the third is caused by a leak in a seamed retort, throughwhich the oxygen blows and sets the retort itself on fire. Such a flaw may be detected by screwing on the arm of the retort, and placing the body part under water and blowing hard down the delivery tube, when, if a leak exists, bubbles will rise from it. fitted with safety valves, which are sometimes a nuisance, and quite unnecessary if the delivery tube has a bore of at least half an inch. I am sure that few who have ever enjoyed the feeling of independence and possessed by those who are their own gas producers, will ever adopt cylinders from choice, though they will always of necessity be used by those who, from one reason or another, are unable to give the few minutes necessary to oxygen making. In conclusion, let me add what may perhaps be a small grain of comfort to cylinder users. I | think it is a German proverb which says, ‘Remember whatever be thy fate that it might and ought to have been worse” ; at any rate it is almost certainly better to be killed by the explosion of an oxygen cylinder, than to perish by the bursting of a pipe containing high pressure steam, as in the former case one is killed instantly, while in the latter the victim is scalded internally as well as externally, and suffers intense agony before death supervenes. Retorts are often | The first may be | self-reliance . Slides for Science Teachers. ELECTRICITY. By E. D. Bartuerr. THERE are a large number of experiments in Electricity in which the apparatus is of such a nature that itcan be made on a small scale and adapted to the lantern easily. By the aid of a small glass tank the principle of a single fluid cell battery can be readily projected upon the screen. A simple piece of apparatus, part of which is illustrated on page 8 of this Journal for January, 1898, will serve the purpose. The drawing Fig, I. shows the arrangement; the base (s) and uprights (x x) are the same together with a suitable glass tank. As the water used in the tank is to be acidulated, care must be taken that the parts are not acted upon, and also that it readily lends itself to be taken to pieces for the purpose of cleansing. The tanks shown in the sketch Fig. I. is very simple in construction and is made by bending a piece of vulcanised rubber between two plates of glass into the shape shown, and then binding them together at the ends with twine. To prevent the edges of the glass from cutting the twine it is as well to somewhat round them upon a piece of flagstone. Across Fig. I. ' the two uprights is a piece of wood (£), held in position by the two projecting pins (HH); a piece of copper and zine (c) and (z) is passed through, which can be either small round rods or sheets with their ends slightly projecting above, but for some distance below. The ends projecting above are connected by wires to the binding screws (ss). The tank is nearly filled with some dilute sulphuric acid H,SO, and the two metal rods placed in position as shown in the drawing. Place the whole in front of the condenser and focus upon the screen. Connect the zinc and copper rods together by two leading wires inserted one in each binding screw, unite