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Spitta writes: 'The idea of employing a wedge of neutral-tinted glass as a photometer has occurred to many observers—Dawes, Captain Abney, and others—and notably of late years to Professor Pritchard, of Oxford, who has produced with such an instrument his well known "Uranometria Nova Oxoniensis", a catalogue of the relative brightness of the brighter stars north of the equator. But the use of such an instrument has always been limited hitherto to the comparison of the relative intensities of such points of light as the stars present, its employment upon objects of sensible area being foreign to the ideas and requirements proposed in its construction. Having, however, attempted to use a photometer of this description upon disks of small but of various areas illuminated by a known amount of light, the discordances of the results forced upon me the necessity of modifying the construction of the photometer in a way which I believe will extend its sphere of usefulness.'

Annotations in pencil and ink. Includes one page of diagrams of plans for the compound wedge photometer.

Subject: Scientific apparatus and instruments / Photometry

Received 8 November 1889. Read 5 December 1889. Communicated by William de Wiveleslie Abney.

A version of this paper was published in volume 47 of the Proceedings of the Royal Society as 'A compound wedge photometer'.

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Earliest possible date
Physical description
Ink and graphite pencil on paper
Page extent
5 pages

Creator name

Edmund Johnson Spitta

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Edmund Johnson Spitta, Paper, 'A compound wedge photometer' by E J [Edmund Johnson] Spitta, 1889, PP/15/3, The Royal Society Archives, London,, accessed on 14 June 2024

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  • Proceedings Papers

    Dates: 1882 - 1894

    The archival collection known as 'Proceedings Papers' is comprised of manuscripts and occasional proofs of scientific papers sent to the Royal Society which were read before meetings of Fellows and printed in full in the Proceedings of the Royal Society.

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