XI. Double refraction and dispersion in Iceland Spar: an experimental investigation, with a comparison with Huyghen’s construction for the extraordinary wave

• Published in: Philosophical Transactions of the Royal Society of London
• Format: Article in Journal/Newspaper
• Language: English
• Published: The Royal Society 1880
• Subjects: Endeavour; Iceland
• Online Access: http://dx.doi.org/10.1098/rstl.1880.0011; https://royalsocietypublishing.org/doi/pdf/10.1098/rstl.1880.0011

In a paper read before the Royal Society, June 20, 1878, the results of an investigation into the truth of Fresnel’s theory of double refraction in a biaxal crystal were stated. The comparison between theory and experiment was made by a method suggested by Professor Stokes (British Association Report, 1862), according to which the reciprocal of the velocity of wave propagation was determined by experiment and also on Fresnel’s theory. The greatest difference between the two amounted to ·0009, and there appeared to be some connexion between the differences and the wave length of the light used. In the endeavour to follow up this connexion I undertook a series of similar experiments with light of different wave lengths, using three lines of the hydrogen spectrum and the sodium line. The extreme smallness of the arragonite prisms I had previously worked with led me to use, at first at least, Iceland spar, which could be obtained in large pieces with ease, and for which the theoretical calculations were greatly more simple. Professor Stokes had already made a series of experiments by the same method with this substance (Proceedings of the Royal Society, vol. 20, p. 443) and arrived at results confirming Huyghen’s construction. The details of his experiments are as yet unpublished, and I venture to think it might be useful to have arranged in tabular form a series of results, to serve in the future as a test of any theory of double refraction which might be proposed. The method of the experiments, as suggested by Professor Stokes (British Association Report, 1862), is as follows: A prism is cut from a piece of spar, and the position of its faces with reference to the cleavage faces carefully determined. The prism is mounted on a spectrometer, and the collimator adjusted so that the rays of a definite wave length falling on the prism are parallel, the edge of the prism being parallel to the axis of revolution of the reading telescope. The deviation of the light passing through the prism in any position is observed, ...