Optical projection: a treatise on the use of the lantern in exhibition and scientific demonstration (1906)

Page scan 000275 from Optical projection: a treatise on the use of the lantern in exhibition and scientific demonstration

Record Details:

Title:
Optical projection: a treatise on the use of the lantern in exhibition and scientific demonstration
Date:
1906
Author:
Wright, Lewis, 1838-1905
Publisher:
London, New York, Bombay : Longmans, Green and Co.
Volume:
Optical projection: a treatise on the use of the lantern in exhibition and scientific demonstration
Leaf #:
000275
Language:
English
Collection:
Books
Format:
Books
Contributor:
University of California Libraries
Sponsor:
MSN
Coordinator:
Media History Digital Library
Date Added:
July 19, 2022
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260 OPTICAL PROJECTION by twitching with the finger. As far as regards the projection, this is cheap and efficient, but is not audible ; it has the advantage, however, of producing the figure by motions of the same kind as a couple of forks. For projecting the figure only, the ap- paratus shown in fig. 137 has been devised by Pfaundler, who de- scribed it in the ' Pro- ceedings ' of the Vienna Academy (of Sciences) and figures it in his * Lehrbuch der Physik.' Fl0 - 136 The vibration of two springs s, s', set rect- angularly to each other, one variable by a weight, L, is given to two discs, D D', with slots which also cross at right angles. The spot of light where they cross, evidently moves in a path com- pounded of the two motions. The discs are arranged in front of the condensers, the spot being focussed as an ordinary dia- gram, and the springs twitched. Stohrer has constructed a more complicated apparatus for giving the same motions to two discs by a wheel and gearing, methods of which will FIG. 137