On Light. 



413 



Index of Refraction, 

 Sulphate of ba- "^ 



rytes, (double >- W. 1-646 



R.) J 



Iceland spar, \ W. 1-657 



(strongest,) J 

 Gum dragon, W. 



Carburet of sulphur, Br. 1*680 

 White sapphire, W. 1'768 

 Muriate of anti- 



mony, variable, J 



W. 



Arsenic, (a good\^ j.gj^ 



test,) J 



Spinelle ruby, W. 1-812 



Index of Refraction. 



Jargon, W. 1-950 



Glass of antimony, W. 1 -980 



Native sulphur, W. 20-40 



Do. Brewster, 2-115 



Plumbago, W. 



Phosphorus, Brewster, 2-224 



Tk- J fNewton, 



Diamond,|j^^p^,^ 2-440 



Do. Rochon, 2-755 



Realgar, Brewster, 2-510 



Chromateof lead.n i nA nn 

 n . c \ >ao. 24*79 

 (least refr.) J 



Do. (greatest refr.) do. 2-926 



Table II. — Refraclmg Poioers of Gases for the Temperature 

 of 32° F. and Pressure 30, ly MM. Biot and Arago. 



Atmospheric air. 

 Oxygen, .. 

 Azote, 

 Hydrogen, 

 Ammonia, 



1-00000 

 0*86161 

 1*03408 

 6-61436 

 2*16851 



Carbonic acid, .. 1*00476 



Subcarburetted hy- 1 2'0Q270 



drogen, J 



Muriatic acid gas, 1*19625 



Cryolite, 

 Fluor spar. 

 Water, 

 Diamond, 



Table 111. — Dispersive Powers. 



Sulphur, Brewster, 0*130 



Oil of cassia, .. do. 0-139 

 Realgar, . . do. 0*255 



Chromate of lead, 



(least refr.) 

 Do. (greatest refr.) do. 0*400 



'} 



do. 0*262 



Brewster, 0-022 



do. 0022 



do. 0*035 



do. 0*038 

 Flint glass, (highest,) do. 0*052 

 Carburet of sulphur, do. 0*1 15 

 Phosphorus, do. 0*128 



Carburet of sulphur exceeds all fluid bodies in refractive power, 

 surpassing even flint-glass, topaz, and tourmaline; and in disper- 

 sive power it exceeds every fluid substance, except oil of cassia, 

 holding an intermediate place between phosphorus and balsam of 

 Tolu. 



Dr. Brewster has further shown, that all doubly refracting 

 crystals have two dispersive powers. 



From Table U. it appears, that the refractive power of hydro- 

 gen gas greatly surpasses not only that of the other gases, but of 

 all known bodies. This principle exists in great abundance, in 

 resins, oils, and gums, where it is united to carbon and oxygen ; 

 and we must probably ascribe to it, the eminent refractive power 

 of these combustibles, so justly observed by Newton. This effect 

 of hydrogen is finely displayed in ammonia, whose refractive power 



is 



