Identifier: s04philosophicalmag05londuoft (find matches)
Title: The Philosophical magazine; a journal of theoretical, experimental and applied physics
Year: 1798 (1790s)
Authors:
Subjects: Physics
Publisher: London Taylor & Francis (etc.)
Contributing Library: Gerstein - University of Toronto
Digitizing Sponsor: Ontario Council of University Libraries and Member Libraries

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bruary; having, in fact, been written previouslyto the writer having seen that article. The two papers obviouslyhave no further connexion than the circumstance of both refer-ring to phsenomena occasionally accompanying rainbows. LXX. Description of a New Pseudoscope. By Walter Hardie, Edinburgh. (With a Plate.) To the Editors of the Philosophical Magazine and Journal. Gentlemen, PERHAPS the following description of a new pseudoscopemay interest those of your readers who have studied Pro-fessor Wheatstone^s and Sir David Brewsters papers upon bino-cular vision. It consists of a simple combination of plane reflect-ors, and may be constructed of pieces of thin looking-glass. Inthe accompanying diagrams these are represented in section bythe thick black lines; the thin lines, representing the visual raysas reflected by the mirrors, will also serve to indicate the positionof the reflecting surfaces. The peculiar properties of this instru-ment are,— PJul. Mcvg. Sei.^. VoL S. PI. V viiA/i-
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Siq. I. fio I Mr. W. Hardie^s Description of a New Pseudoscope. 443 1st. It exhibits the pseudoscopic image either reversed, or inits true aspect, each of these appearances being instantaneouslychangeable into the other at pleasure. This change is effectedby the alternate removal and replacement of the mirrors a, b(Plate VI. fig. 1). When these are removed, the visual rays ofthe two eyes are transposed; and being twice reflected, the imageof course is not reversed. When they are replaced, the rays arenot transposed; but being now thrice reflected, the image isreversed. In both cases the pseudoscopic phseuomena are exhi-bited, but not equally well in cases where the mode in which theobject is illuminated is unfavourable, namely, where a side-lightoccasions corresponding shading. In objects thus illuminated,the conversions of relief are more easily seen with the reversingarrangement than with the other. This seems to arise from thereversed position of the shading corresponding in some d

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