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

Page scan 000343 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 #:
000343
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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H2$ OPTICAL PROJECTION Sometimes the heat of the lantern will destroy the film too rapidly. In that case an alum cell in the slide-stage will remove the difficulty. Horizontal bands being caused by the action of gravitation on the film, if we can make the gradual thinning take a circular form, the bands will become annular. This is effected by a beautiful modification of the experiment often employed by Lord Eayleigh, and which is very easy if any sort of bellows, or weighted bag filled with air, be at hand, to furnish a slight blast. Even the breath will answer, but needs some practice and a thin rubber balloon to steady the pressure. Connected with the air-blast (a gentle one) by rubber tubing is a piece of glass tube drawn into a small but A B FIG. 180.—Rotating Films not capillary orifice: one of the ' fillers' sold for use with fountain pens answers excellently. This is fixed in another small Bunsen holder, and adjusted so as to direct a blast at a small angle with the surface of the film. Adjusted near the edge as at A (fig. 180) the above is converted into a single whirling vortex, which shows rapid and magnificent gradation of colour: adjusted as at B, a little to one side of the centre, the stream divides into two vortices, in which the play of colour is still more rapid. This experiment never fails to 'bring down the house.' 187. Films of air—Newton's Rings.—Two squares of plate glass, with rounded edges, cleaned and polished, are readily