. Optical projection : a treatise on the use of the lantern in exhibition and scientific demonstration. p and a length of rubber tubing, andis so white and clean, that in small halls and class-rooms, where adisc of 8 or 9 feet suffices, it is, and will be, deservedly popular. The complete fitting, including mantle and burner, with a con-cave reflector, is now sold at prices varying from 7s. Qd. to 10s.,and can be had of all leading opticians. Incandescent Spirit Burner.—This is a burner essentially thesame as the above, but using methylated spirit instead of gas, vS^~ APPENDIX 419 for use in s
. Optical projection : a treatise on the use of the lantern in exhibition and scientific demonstration. p and a length of rubber tubing, andis so white and clean, that in small halls and class-rooms, where adisc of 8 or 9 feet suffices, it is, and will be, deservedly popular. The complete fitting, including mantle and burner, with a con-cave reflector, is now sold at prices varying from 7s. Qd. to 10s.,and can be had of all leading opticians. Incandescent Spirit Burner.—This is a burner essentially thesame as the above, but using methylated spirit instead of gas, vS^~ APPENDIX 419 for use in small halls where the latter is not available (fig. 234).The burner is cheap (about 12s. €>d.) and simple and easy to use,but the light is not as good as even the gas-burner, and hence isuseless for discs above 7 to 8 feet in diameter. There is a class of incandescent spirit lamps similar to this, butin which the spirit is put under pressure, either by raising thereservoir a few inches, or by pumping air into it, with the resultthat the light is considerably increased; but these can hardly be. Fio. 234.—Incandescent Spirit Burner recommended for amateur lanternists, as, if 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 mod
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Keywords: ., bookauthorwrightle, bookcentury1900, bookdecade1900, bookyear1906
