Machinery and processes of the industrial arts, and apparatus of the exact sciences (1869)
Barnard, Frederick A. P. (Frederick Augustus Porter), 1809-1889 · Washington, Govt. print. off. · leaf 557
they proceed from points more and moredistant from the axis. And inasmuch as with the higher powers thecross dimensions of all the pencils are proportionally reduced, it followsthat a division which must necessarily take place at some distancebehind the innermost glass of the objective will become… … This disadvantage led to the suggestion, two ore1 three years ago, by Mr. Wenhain, of a method ofdividing the pencil by the interposition of a transpa-rent plane reflector, which, by being adjusted to aproper inclination, might reflect one half the light ofeach pencil, and allow the other half to…
Machinery · Scientific apparatus and instruments
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