Optical projection : a treatise on the use of the lantern in exhibition and scientific demonstration / by Lewis Wright.

  • Wright, Lewis, 1838-1905.
Date:
1901
Catalogue details

Licence: Public Domain Mark

Credit: Optical projection : a treatise on the use of the lantern in exhibition and scientific demonstration / by Lewis Wright. Source: Wellcome Collection.

    62/488 (page 50)
    28. Adjusting Oxy-gas Jets.—These forms of jet will easily give 200 candles, and with care have reached 250 candles, and more. In many cases, however, they never give what they might for want of a proper adjustment, which is a matter of more nicety with them than with mixed-gas jets. The same remark applies to oxy-spirit jets, and the adjustment is practically the same in both cases. The most general error is to use too much weight on the bag. It seems considered the correct thing to put on a 56-lb. weight in any case, but in many instances 28 lbs., or only a few lbs. beyond, will give a better light, and the too fast rush of the oxygen through the gently-emitted hydrogen actually cools the lime. The distance of the lime from the jet is also all-important. These points cannot be adjusted in the lantern, as every change in position there affects the optical adjustments also, and thus disguises the result as regards brilliance. The jet should therefore be taken out of the lantern, and placed so that its naked illuminating effect upon the screen or a wall can be seen. Then experiments should be deliberately made : first as to oxygen, and then as to the distance of the lime from the orifices. This will probably not differ much either way from half an inch ; but it will be found that an eighth of an inch will make a great difference. At each change in distance, however, 't may be found that a different flow of the gases gives a better light at that distance ; and it has to be ascertained what distance, properly adjusted by tap and pressure for its proper flow of gas, gives the best light. That is the adjustment for this particular jet, and, once made, is made once for all. It is, therefore, worth while to take trouble over it. What are sold as 1 soft ’ limes are best for oxy-gas as well as spirit jets, but ‘ excelsiors ’ do also very well. The lime is little acted upon by the comparatively moderate heat, and a lime-spindle which can be turned by a milled-head underneath, as in fig. 31, will answer if economy is desired. But any of