. Optical projection : a treatise on the use of the lantern in exhibition and scientific demonstration. f the temperature of thevolatilising chamber should fall too low, the spirit is apt to overflowinto the lantern and catch fire, and though this may seldom happenthe risk is a high price to pay for the extra light, particularly as abrilliant light can now be obtained from acetylene without anydanger. Acetylene Gas.—This illuminant has made immense stridesduring the last few years, and has now to a very large extentsuperseded oil lamps, and has even made great inroads upon thepopularity of lim
. Optical projection : a treatise on the use of the lantern in exhibition and scientific demonstration. f the temperature of thevolatilising chamber should fall too low, the spirit is apt to overflowinto the lantern and catch fire, and though this may seldom happenthe risk is a high price to pay for the extra light, particularly as abrilliant light can now be obtained from acetylene without anydanger. Acetylene Gas.—This illuminant has made immense stridesduring the last few years, and has now to a very large extentsuperseded oil lamps, and has even made great inroads upon thepopularity of lime-light. A 1 lb. tin of carbide of calcium can beobtained for about 6d., and on being mixed with water will give off e e 2 420 OPTICAL PROJECTION enough gas to supply a lantern acetylene jet for nearly two were at first difficulties in consequence of the explosive pro-perties of the gas, but now all modern lantern generators are soconstructed that they only produce the gas in very small quantitiesas required, and under no circumstances should there ever beenough to cause an Fig. 235.—Acetylene Generator The number of these generators on the market at present ialegion, and it would be useless to attempt to describe them. They may practically all be divided into two classes : those inwhich the carbide drops a little at a time into the water, and thosein which the water is gradually admitted to the carbide, which, inthis form of generator, is usually placed in small trays or cells. •? /,., APPENDIX 441 It is claimed for the first pattern that the gas evolved is coolerthan when the water is admitted to the carbide. There doesappear to be some advantage in this respect, but the admission ofcarbide, which is usually in small lumps, is difficult to control, andon the whole the plan of gradually admitting water to the carbideis now generally followed. A typical lantern generator is shown above (fig. 235). As willbe seen, it acts on the gasometer principle,
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Keywords: ., bookauthorwrightle, bookcentury1900, bookdecade1900, bookyear1906
