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Societies and Academies

Nature volume 113, pages 662663 (03 May 1924) | Download Citation



LONDON. Optical Society, April 10.—H. Dennis Taylor: The feasibility of cinema projection from a continuously moving film. The film picture may be reflected from a series of mirrors suitably mounted on a drum which is rotated at a definite speed relative to the motion of the film. The various oscillations that may be introduced on the screen image can be minimised or eliminated. As compared with the usual type of projection, continuous projection results in a considerable saving of light, much reduced wear and tear of the film, complete freedom from light and dark flickering and consequent eyestrain, and much greater quietness in running.—E. Wilfred Taylor: A new, perfectly anallatic internal focussing telescope. In all surveying instruments, where the distance of an object is deduced from the stadia intercept, the distance so obtained is referred to the “anallatic point,” situated either on the axis of the telescope or on the axis of the telescope produced. The introduction of the anallatic lens by Porro automatically referred all distances, deduced from the stadia intercept, to the centre of the instrument, since the latter coincided with the anallatic point. The internal focussing telescope has now been adopted by most instrument makers, and, as the position of the anallatic point varies, a small but variable correction must be made in order to refer distances to the centre of the instrument. A new telescope is now described which, while perfectly anallatic, is of the internal focussing type, and combines the advantages of the Porro construction with those of the internal focussing telescope.

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