. Optical projection : a treatise on the use of the lantern in exhibition and scientific demonstration. not even and good with such attach-ments, unless pains aretaken to accurately adjustthe first reflector as re-gards the parallel (orslightly diverging) raysfrom the lantern con-densers. To ensure thisthe lantern itself is oftenfitted up by Hawkridge,and other American opti-cians, as in fig. 91. Herethe two first lenses ofa triple condenser aremounted in the body ofthe lantern, which is sup-ported on pillars; whilethe third or converginglens is fitted in a platehinged to the top of thelantern
. Optical projection : a treatise on the use of the lantern in exhibition and scientific demonstration. not even and good with such attach-ments, unless pains aretaken to accurately adjustthe first reflector as re-gards the parallel (orslightly diverging) raysfrom the lantern con-densers. To ensure thisthe lantern itself is oftenfitted up by Hawkridge,and other American opti-cians, as in fig. 91. Herethe two first lenses ofa triple condenser aremounted in the body ofthe lantern, which is sup-ported on pillars; whilethe third or converginglens is fitted in a platehinged to the top of thelantern front. This platefig. 91 has at one side a pillar or standard, which carriesthe focussing power and second reflector. For vertical work,the lantern is arranged as in the diagram, the front plate andlens being supported in a horizontal position by a movabletriangular box, to whose hypotenuse side is fixed the reflector;but when ordinary work is required, this box is removed, whenthe plate drops down to a vertical position, with the focussingpower out in front as usual. The second small reflector is. APPARA TUS FOR SCIENTIFIC DEMONSTRA TION 169 then removed, when the lantern projects direct. Several ofthese lanterns have reached England ; but there seems asort of national fashion in apparatus, and so far as I amaware, they are thought rather awkward in use by their pos-sessors. Messrs. Newton & Co. have constructed a bi-unial lantern
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Keywords: ., bookauthorwrightle, bookcentury1900, bookdecade1900, bookyear1906
