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On a new method for studying the optical properties of crystals1

Published online by Cambridge University Press:  14 March 2018

Henry Clifton Sorby
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Extract

Before treating of the subject before me, I must describe its history. At a soirée of the Royal Society on April 25, 1877, I showed a number of specimens illustrating a new class of optical properties, applicable to the identification of minerals. These greatly interested the late Sir G. G. Stokes, Bart., and led to a considerable amount of correspondence between us ; and he communicated a paper to the Royal Society on the mathematical part of the subject, and I sent a short one on my apparatus and observations. This was admitted to be very imperfect, since the crystals examined, though showing the general facts perfectly well, had not been cut so as to be suitable for such quantitative measurements as could be compared with Stokes's theoretical determinations.

Type
Research Article
Information
Mineralogical magazine and journal of the Mineralogical Society , Volume 15 , Issue 70 , July 1909 , pp. 189 - 215
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 1909

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Footnotes

1

The MS. of this paper was finally prepared for press by Dr. Sorby during his last illness. It contains the details and complete account of his work, of which preliminary accounts were published in the first two volumes of the Mineralogical Magazine under the following titles :-

‘On a simple method of determining the index of refraction of small portions of transparent minerals.’ 1877, vol. i, pp. 97-98.

Presidential address. [Determination of refractive indices in mineral plates, &c.] 1877, vol. i, pp. 193-208, with plate VII.

‘On the determination of minerals in thin sections of rocks by means of their indices of refraction.’ 1878, vol. ii, pp. 1-4.

Further improvements in studying the optical characters of minerals.’ 1878, vol. ii, pp. 103-105.

The method he describes for determining refractive indices is identical in principle, though worked out in far greater detail, with that given by the Duc de Chaulnes in 1767 for singly-refracting substances ; but, as may be gathered from a remark in the last of the papers quoted above, the method was devised quite independently by Dr. Sorby.

The paper is now published with the aid of a grant from the Government Publication Grant administered by tim Royal Society.

An obituary notice, with portrait, of Dr. Sorby appearcd in the last number of this magazine (vol. xv, p. 180).

References

Page 190 note 1 Stokes, G. G., ‘On the foci of lines seen through a crystalline plate.’ Proc. Roy. Soc. London, 1877, vol. xxvi, pp. 386–401.CrossRefGoogle Scholar

Page 190 note 2 H. C. Sorby, ‘On some hitherto undeseribed optical properties of doubly refracting crystals.—Preliminary notice.’ Ibid., pp. 384-386.

Page 215 note 1 Dr. Sorby's MS. contains no exp]anation of figs. 6 and 7 ; those now given being taken from Min. Mag., 1877, vol. i, p. 200. All the above figures were first given in Plate VII of that volume, and they are reproduced here for convenience of reference.