80 Intelligence and Miscellaneous Articles* 



also diminishes, but diminishes in an irregular manner. It is in fact 

 seen that the green of the spectrum between F and D diminishes less 

 than the red part between D and C, even in absolute value and though 

 it is more spread out : the green contracts less, then, than the red. 



This fact is again met with in Dale and Gladstone's numbers, 

 although they are different from mine. With their numbers it is 

 seen that between A and D the dispersive power diminishes continu- 

 ously, and between D and H this power seems to remain constant, or 

 to diminish very little towards 30 degrees. It is moreover seen that 

 from former experiments Mr. Barlow had found that the dispersion 

 of bisulphide of carbon increased with the temperature (1829). 

 Bisulphide of Carbon saturated with Sulphur, 



C„. D„. F n . D M -0„. F»-D„. 



14 1-6809 1-6917 1-7202 108 285 



24 1-6733 1-6835 1-7118 102 283 



The introduction of sulphur into bisulphide has the effect of in- 

 creasing the refractive index and the dispersive power. Under the 

 influence of heat these elements diminish, and the irregularity of the 

 variation of the dispersive element is even more sensible than in the 

 preceding substance. 



With bisulphide almost saturated with phosphorus it seems that 

 while the red part contracts, the green part of the spectrum expands. 

 F„ — D n varies from 298 to 309, from 15 to 25 degrees of temperature. 



From the whole of these results presented by these three liquids, 

 it may be concluded that the dispersion of bisulphide of carbon varies 

 irregularly under the action of heat, and that the green part con- 

 tracts much less than the red part ; if the bisulphide be rendered 

 more refracting and dispersing by solution of sulphur or of phos- 

 phorus, this irregularity will be more and more pronounced, so that 

 we might arrive at a liquid in which the two parts of the spectrum 

 would vary in contrary directions. 



Glycerine. 

 C«. D„. F H . 



8.... 1-46591 1-46796 1-47368 



99.... 1-44246 1-44454 1-44976 



This substance seems to differ from the preceding substance. 

 Here the dispersive power still varies in an irregular manner ; but 

 the red part remains equally dispersed (the preceding numbers only 

 giving a slight augmentation), and the green part contracts very 

 appreciably. 



I have also worked with many other liquids, and have ascertained 

 that they may always be ranged in one of the preceding groups. 

 Each liquid seems to behave in a special manner. In the greatest 

 number of cases, such as aqueous solutions, alcohol, &c. the dispersion 

 diminishes regularly, and the two coloured parts mentioned here 

 contract almost equally ; the dispersion of others, such as bisulphide 

 of carbon, anhydrous chlorides, varies irregularly, and the green part 

 of the spectrum contracts much less than the red one ; in others, 

 finally, like glycerine and hydrochloric acid, the dispersion still varies 

 irregularly, but the red part contracts less than the green one. — 

 Comptes Rendus, May 20. 



D»-C n . 



Fn-D, 



205 



572 



208 



522 



( AC 



3 '°"7 



