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Knight's Mechanical Encyclopedia (ed. Knight) 2 0 Browse Search
Medford Historical Society Papers, Volume 7. 2 0 Browse Search
Medford Historical Society Papers, Volume 8. 2 0 Browse Search
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Knight's Mechanical Encyclopedia (ed. Knight), M. (search)
s ago by Mr. Wenham of a method of dividing the pencil by means of a transparent plane reflector, which, adjusted at a proper angle, might reflect one half the light of each pencil, allowing the other half to pass through. This plan involves the loss of the stereoscopic effect, but secures to the observer the satisfaction of using both eyes in viewing an object. It has, however, proved somewhat difficult to carry out this idea satisfactorily in practice. See prism. Messrs. Powell and Lealand of London have patented an arrangement, consisting of a quadrangular prism which receives the rays, part of which pass through, while the remainder are reflected to a triangular prism which transmits them to the eye. This has the disadvantage of causing the object to appear unequally illuminated in the two tubes. Mr. R. B. Tolles has constructed an instrument designed to remedy the defects of the original binocular microscope, at the same time permitting the ordinary single-tubed instrum