The Optical Magic Lantern Journal (February 1890)

70 Tho Optical Magio Lantern Journal and Photographio Enlarger. To operate this instrument, it is merely necessary to wind up the clockwork oncea week (the glass being turned up and down by its agency at stated hours) when each slide contained in the disc will, in turn, be presented upon the screen for about half a minute. A company has been formed to introduce this novel and effective means of advertising. The optical portion of the apparatus is now being constructed and arranged by Mr. W. Chambers, of Featherstonebuildings, Holborn. —10: —_—_ The New Limelight. UF till recently the only means of obtaining a powerful light for the lantern was the oxy-hydrogen limelight, maintained by the consumption of two bulky gases— oxygen and coal-gas—stored in gas-bags. The modem system of compressing gas into cylinders has increased the portability and convenience of oxygen, without adding much to the cost ; but compressed coal gas is considerably more expensive than the former plan of using gas bags. In order to avoid this expense, attempts have been made to replace coal gas by some liquid, which is easily vapourised. ‘These attempts have resulted in ether saturators being put onthe market. The earlier vessels were imperfect, explosions occasionally took place, and ether saturation fell into disrepute. A scientific champion then came to the rescue, in the person of Rev. T. F. Hardwick, who invented the pumice chamber, which was found proof against the penetrating oxy-hydrogen flame. Then Mr. Ives, of the United States, patented in that country (but not in this, I believe) a saturator consisting of two cylinders containing rolls of flannel, which was found to be safer than unstuffed vessels. The fluids used with these saturators were of the most volatile description, viz., ethers boiling under too deg. Fahr. The common ether did not give Satisfactory results, so petroleum ether and anesthetic ether of low boiling points and high prices are now * recommended. These volatile and expensive liquids are hard to get and risky to keep. ; the railway companies do not care to carry them, and practically they are only available for single lanterns. In warm rooms, and with jets of small bore, armed with pumice protectors, dissolving can be accomplished, but as a rule, persons possessing ether saturators prefer using them with single lanterns. A want is thus felt in lantern circles for a saturator which is suitable for dissolving, which cannot explode. which is not liable to give pops or cracks, which is simple in its working, and which will yield a. brilliant light by the consumption of some fluid that is cheap and easy to procure. This want I have endeavoured to satisfy by means ofan improved apparatus capable of being used with any inflammable liquid boiling under 200 deg. Fahr., and which has been styled the Warm Bath Benzoline Saturator. It seems a very simple idea to gently warm a stuffed vessel containing benzoline, with the view of increasing the amount of vapour imparted to oxygen gas passed through ; but this idea was so hard to hit, that a year’s experiments in leisure hours were requisite _ before success was achieved. Starting with the notion of boiling benzoline, ané devising sundry pieces of apparatus for the purpose, a boiling-water bath was finally adopted for applying heat safely to the benzoline vessel. On being tested, the boiler proved an utter failure, for it was quite incapable of producing benzoline steam; but _by a fortunate arrangement of air-tubes in the interior of the vessel, it was found to be an excellent saturator. Air blown through the tubes became heavily charged with inflammable vapour, and could be burnt asthough it were coal-gas. After a series of experiments deemed necessary to, test the safety of the vessel, the results of which were satisfactory, the apparatus was connected to the mixed gas jet of a single lantern, in the manner customary with ether saturators. A happy surprise was in store for the experimentalist. No increase of light had been anticipated, but as soon as the jet taps had been adJusted, the extreme brilliancy of the picture on the screen showed at once that the coal-gas limelight, hitherto deemed the most powerful illuminant for the lantern, must now take a back seat, while the benzoline limelight came to the front in its place. These early experiments were conducted out of doors in summer evenings, with great precautions against accident, for the operator had once been rendered Aors de combat by an ether saturator, and he was disinclined to go through a similar experience on behalf of benzoline. However, not the smallest accident occurred, and confidence became established by degrees, every possible test being applied with the view.of securing that most important virtue in lantern apparatus—immunity from accident. The saturator was far from perfect in its early form, but a refining process took place, in which a certain gentleman, well known in scientific circles, lent valuable assistance by correspondence. He pointed out its weak points, and gave valuable information relating to benzoline and other fluids. Several vessels on the warm bath principle, diftering in design, were successively tested ; the principles necessary for a good saturator were found out ; the nature of the stuffing and disposition of the air tubes was investigated ; while the source of heat provided material for many experiments. To make a long story short, the saturator now consists of a copper vessel stuffed with wool, and furnished with gasways through the stuffing. This is placed within a case somewhat larger, leaving an annular space between the vessels, which is filled with warm air supplied by a night-light burning ina separate chamber placed alongside the air bath. A heat of about ninety degrees Fahr. is maintained in the air-bath. The working of the warm-bath saturator is of the very simplest description. The stuffed copper vessel is charged with fluid, and the surplus liquid drained off. The night-light, which is capable of burning six hours without attention, is lit ; the three brass nozzles fixed on the top of the saturator are connected by rubber tubing, the one to the top of the cylinder or gasbag, the others to the jet taps, or in the case of a biunial to the nozzles of the dissolving tap. Nothing more need be done to the saturator; the lantern operator can devote all his attention to other matters, while his manipulation of the jet taps and dissolver is precisely the same as with coal-gas. ALBERT WM. SCOTT.