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

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 #:
000362
Language:
English
Collection:
Books
Format:
Books
Contributor:
University of California Libraries
Sponsor:
MSN
Coordinator:
Media History Digital Library
Description:
Date Added:
July 19, 2022
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LANTERN POLARISING APPARATUS 34? re-reflected into a horizontal direction and polarised by the pile P with a black glass at the bottom. This arrange- ment can be made cheaply and readily of any size desired. It will be observed, that while the horizontal direction of the beam from the lantern is preserved in the Delezenne polarisers, it is necessarily deflected several inches to one side of the axis of the flange-nozzle. In the first instruments made on this principle, the beam was brought down below the nozzle; but this makes the apparatus rather deep, and requires a deep case for packing. To avoid this the polariser FIG. 194.—Direct Reflecting Polariscope was turned sideways ; but that was found awkward, and also necessitated a large case. To meet these objections I advised reversing the polariser so as to deflect the beam upwards, and Messrs. Newton & Co. now construct their instruments as in fig. 194. It will be seen that it is then rendered quite compact, and requires no larger a case than the Nicpl prism polariscope. All the front portion is precisely the same as in the instrument shown in section in fig. 190. Such polarisers are liable to the same objection as the elbow form, not being capable of rotating the polarised beam* This can, however, be effected through a simple expedient suggested by Professor S. P. Thompson. If we cause the po- larised rays to pass through a mica quarter-wave plate (§ 211)