XIV. Researches on the refraction, dispersion, and sensitiveness of liquids

Abstract

In a previous paper “On the Influence of Temperature on the Refraction of Light,” we started some inquiries which have been since pursued, and we now lay before the Royal Society some of the later results. The same apparatus has been employed, with a hollow prism of 61° 0' angle, and the method of observation has been essentially the same. But experience has led to some modifications, the most important of which is this: instead of attempting to take the angular measurements at certain foredetermined temperatures, as 10° C., 20° C., they were taken first at the temperature of the room, whatever that might be, and then at such other temperatures as seemed to offer the most trustworthy results. This involved more calculation, but it still saved time, and secured greater accuracy. The plan of measuring to 10" was abandoned as a useless nicety; but, as a rule, two or more observations of each fixed line at each temperature were taken, and if they differed slightly the mean was adopted, but if the discrepancy amounted to 2' or 3' the observation was repeated. The average of these observations of the lines A, D, and H at different temperatures gave the refractive indices which are placed together in the Table that constitutes Appendix I., and they afford the data for nearly all the comparisons about to be instituted. Appendix II. contains the mean determinations made of the refractive indices of some of these liquids for a larger number of the lines at the temperature of the room. To it have been added some observations on other liquids, and deter­minations published in our former papers, so as to render it as complete as possible for any who may desire to investigate the irrationality of the spectrum, or the truth of the formulae of Cauchy.