262 Scientific Intelligence. 
will be remembered, is of this kind: first, that the metals (an 
tallic sulphurets, &c.) have no angle of complete polarization for com- 
mon light; and secondly, that a plane polarized ray becomes elliptical- 
ly polarized after reflexion from their surfaces, whereas it remains plane 
olarized after reflexion from glass and such like bodies. Endeavors 
have naturally been made to account for these phenomena on the prin- 
ciples of the undulatory theory ; and always, apparently, on the sup- 
position, that the laws of reflexion from transparent (uncrystallized) 
bodies were already rigorously given by Fresnel’s formule, but that a 
new and distinct theory was required for metallic reflexion. Thus as- 
spect. o not know that any writer, except Mr. Green, (in 
and harmony with the new result which I have now to state. It con- 
sists in this: that these same highly refractive substances resemble the 
metals also in a second respect—that they confer elliptic polarization 
on a plane polarized ray reflected from them. e following list of sub- 
stances, in which this property was observed, will be found to contain 
most of those at the top of Sir D. Brewster’s list of refractive indices :-— 
Indigo—which is remarkable for possessing the metallic lustre with- 
Artificial realgar. 
iamond—of which three specimens were tried. 
Sulphuret of zinc in transparent crystals. 
Glass of antimony—translucent. 
Sulphur—melted on a polished slip of zine foil. “ai 
Tungstate of lime—transparent. nis 
Carbonate of lead in crystals, clear and limpid:as glass. 
Hyacinth, or zircon—translucent. 
Arsenious acid. 
Garnet. 
ocrase. 
Helvine. Labrador hornblend. 
