182 S. Webber on Ventilation. 
compound forms of 6 crystals, plagihedral in character, have 
been observed, and a figure is given in the paper 
_- The Humite occurs mostly either in foliated or granular lime- 
stone, or in a peculiar kind of granitic rock along with white 
olivine, mica and magnetite. In the former of these rocks the 
crystals are of the 2d or 3d type, and in the latter of the Ist or 
3d. The color for each type varies between brown, reddish 
brown, yellow and white. G.=3-2; of a white crystal of the 
3d, 3°186; a yellow of the 2d, 3-177. H.=6—65. The mineral 
is easily soluble with muriatic acid when pulverized. The iden- 
tity of Humite with Chondrodite in chemical constitution was 
shown by Prof. ©. Marignac, who also investigated with much 
labor the crystallography of the species, and distinguished three 
types among the crystals. He failed however of detecting their 
true relations, owing to his making e? of figs. I and If homolo- 
gous planes, and r* of fig. I identical with r° of fig. IL ~ 
* 
Arr. XXI.—Further Remarks on Ventilation and the Warm- 
ing of Rooms; by S. Wrsner, M.D., Charlestown, N. H. 
of warming it in cold weather will be nearly that mentioned by 
Professor Hosking as a plan of recent origin, though from the 
writers recollections it was shown to have been used in this 
country nearly fifty years ago. This is, to have an open fire~plac®: 
adapted for either wood or coal, as either kind of fuel may be 
most convenient, with a hollow hearth, sides and back, into W9~" 
hollows air shall be admitted by a pipe leading from the ope? ed 
outside of the building, and which, when warmed by copie” 
with the heated sides of the fire-place, in contact or nea 
with the fire, shall pass out into the room by openings in ont Re 
gt Folune xii, page 874 
a 
