@.U, Shepard—Corundum of N. Carolina and Georgia. 175 
ones atoms,—and these in their turn can give rise to con- 
_ results, as when we gradually raise the temperature of a 
-J9stance the oscillating movements of its molecules are 
mparted to the ether, and waves of less and less length are 
successively engendered. 
she remark has been made that these results are essentially 
sean with photometry. In fact, any thermometer is con- 
"ted into a photometer, if its ball or other receiving surface 
be coated with a perfectly opaque non-reflecting substance. 
ae ae ea 
sa XXIV.—On the Corundum region of North Carolina and 
b corgia, with descriptions of two gigantic crystals of that species ; 
oy Cartes UpHam Sueparp, Sr., Prof. of Natural History 
jm Amherst College, Mass. 
(Concluded from page 114.) 
ey remains to speak of the corundum itself. This may be 
'd to be eminently crystalline throughout, often in tolerably 
ead crystals of considerable size, in a few instances, gigantic. 
er form, as usual, is that of six-sided prisms or pyramids, 
Sometimes the two combined; and exhibiting occasional trian- 
gular faces belonging to the primary rhombohedron. Whether 
