Optical projection : a treatise on the use of the lantern in exhibition and scientific demonstration / by Lewis Wright.

  • Wright, Lewis, 1838-1905.
Date:
1901
Catalogue details

Licence: Public Domain Mark

Credit: Optical projection : a treatise on the use of the lantern in exhibition and scientific demonstration / by Lewis Wright. Source: Wellcome Collection.

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    fcion two images of the jar, formed by rays at right angles with those direct from the jar to the spectators. The great advantage of this method is, that the spectators only need to be about the same height as the jar, to receive perfectly polarised light all round; and the complementary effect can always be seen at the same moment in the mirrors, so that when the jar extinguishes direct light, the mirror images are bright. This having been demonstrated, we finally cover the top of the jar with a large quartz plate Q. The jar itself will now glow with all the rotational colours as the polariser is rotated; differently-coloured images being seen at the same time in the mirrors m, and the whole forming a demonstration of indescribably delicate beauty. It is convenient to have the mirrors hinged together like a book, and to stand both jar and mirrors on a circular piece of board, if no higher support be needed, in order that the whole may be turned to face in succession all sides of the room. CHAPTER XXIII HEAT A numbee of experiments showing the effects, nature, and qualitative relations of heat are easily capable of projection. Some specimen examples may suffice. 224. Expansion.—As regards the expansion of solids, Gravesande’s ring and the various socket forms of apparatus need no remark. Any ordinary form of pyrometer is readily projected in action by the shadow method (§ 109) ; or a small