Snelling, Henry Hunt, 1816-1897 · [New York : W.B. Smith] · leaf 352
r region of the sky to whichit may be considered desirable to limit theobservation, and which is admitted, as inthe other case, through a fine slit in thecover of the instrument. Mr. Jordan has devised an instrumentfor numerically registering the intensityof the incident beam, which appears tohave… … r/jmv:jr- r-7ai«^::lii 44 interior one is fixed to the axis and doesnot revolve, being merely the support of theprepared paper; the interior cylinder ismade to revolve about this once in twenty-four hours by a clock movement. It has atriangular aperture cut down its wholelength, as shown in the…
Photography · Art and photography
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