Refractive Powers of several Bodies. 29*? 



Rochelle salt (mean green rays,) - - 1.4985 



. . (mean red,) - - - . 1.4929 



English plate glass (extreme red,) - - 1.513S 



Crown glass, a prism by Dollond (extreme red,) 1.526 



another do. do. - 1.5301 



Apophyllite (leucocy elite,) _ - - 1.5431 



Hyposulphate of lime (mean red,) - - 1.561 



. (mean yellow green,) - 1.566 



Flint glass, - - . _ - 1.578 



' a prism by Dollond - - > 1.589 



. (extreme red,) - 1.585 



I a prism by Dollond (extreme red,) - 1.601 



do. marked " heavy" (extreme red) - 1.602 



Hyposulphite of lime, least refraction, - - 1.583" 



greatest refraction, - 1.628 



■ strontia, least refraction, - - 1.608 



greatest refraction, - 1.651 



Sulphate of barytes, ordinary refraction (along the axis) 



for yellow green rays, _ - - 1.6460 



. another specimen do. red rays, 1.6459 



for yellow green rays, - 1.6491 



Chloruret of sulphur, . _ _ - 1.67 



Nitrate of bismuth, least refraction about - 1.67 



■ greatest about - 1.89 



\ Hyposulphite of soda and silver, least refraction, 1.735 



. __ greatest do. - 1.785 



Spinelle ruby, . - - - 1.756 



Rubellite, ... - - 1.768 



Labrador hornblende, - - - - 1.80 



Silicate of lead, atom to atom, - - 2.123 



Nitrate of lead (bioxal, ? quadro-nitrate) or six-sided 



prisms, ordinary refraction, . - - 2.322 



At the end of the table from which the preceding measures 

 are taken, Mr Herschel has made the following appropriate 

 remarks. 



" In casting our eyes down the foregoing table, we cannot 

 but be struck with the looseness and vagueness of those re- 

 sults which refer to bodies whose chemical nature is in any 

 respect determinate. The refractive indices assigned to the 



