eR OD See Ieee BP ont A rh gt ed ae el ee ee See aie ee 
G. W. Hawes—Liquid Carbon diowide in Smoky Quartz. 207 
large as formerly, and the one to the right becoming correspond- 
ingly small. A part of the water had been transferred therefore 
to the right hand chamber 
Many cavities, especially those in well-developed crystals, are 
bounded by planes parallel to the outer planes of the crystal. 
uch are represented in figs. 11 and 12, These usually appear 
dark in color, by transmitted light, because so much light is’ 
reflected away by the crystalline planes. Their inclusions are 
frequently better seen by reflected light. These cavities attain 
sometimes to a diameter of two millimeters. 
_A fragment of Branchville quartz as it appears when magnified twenty-five 
diameters, 
Fig. 18 represents the general appearance of the rock, as 
seen with a low magnifying power, a cavity 1™™ in diameter 
being in the field. Such a bubble as this cavity contains will 
contract when heat is applied, but before it disappears the crit- 
leal temperature will be reached when the bubble will expand 
and occupy all the space of the two inner zones. e most vio- 
lent ebullition will oceur when the section cools to the critical 
temperature. A multitude of small globules will appear, and 
will finally unite, and the reverse processes of contraction and 
€xpansion will follow. i 
he character of the included gas has been determined by 
Professor Wright, who gives the results of his investigation in 
another article. ie aci 
_ Having observed bubbles both in liquid carbonic acid and 
in water that were in rapid erratic motion, the old question of 
the cause of these motions was suggested. The lack of a con- 
clusive explanation of these movements has never been felt 
