Microscopical Light in Geological Darkness. — CI ay pole. 217 
pected from work at the head of the lake, for the Stehekin 
river, which occupies the continuation of the valley to the 
west, has been filling in the head of the lake for a consider- 
able time and has shortened its length by several miles. 
No account of the ice work in Okanogan county would be 
complete without some reference to its present glaciers, — the 
residual members of the old ice system. Little has, however, 
been done to explore the ice fields which occupy the rugged 
region to the north and west of lake Chelan and the Methow 
river. Prospectors report them as being numerous through- 
out tlrat country. From the summit of a high mountain west 
of Chelan, Wright's peak, itself bearing a small glacier, I have 
looked off upon a region where they might be counted by the 
score. Some of the central mountains seem to be completely 
covered with ice and snow, except for the aiguilles which 
pierce through. Although moist conditions still prevail, it is 
probable that we are witnessing a period of slow retreat. 
MICROSCOPICAL LIGHT IN GEOLOGICAL 
DARKNESS.* 
By E. W. Claypole, Akrou, O. 
Gems and other crystals had long been known, especially 
•since the time of Brewster, to contain minute cavities partly 
or entirely filled with a liquid whose nature was unknown. 
But by the study of a few specimens Sorby succeeded in de- 
termining it in several cases. Among these was one which 
deserves to become classic on account of the peculiar advan- 
tage which it gave to our pioneer in the investigation. This 
was, indeed I hope I may say it is, though I do not know its 
present abode, a sapphire containing a cavity of a tubular 
form. It was so regular in its bore that it served the pur- 
pose of a natural thermometer, and by its use Mr. Sorby 
reached a conclusion at once surprising and important. I 
should mention that this little thermometer was one-fourth 
of an inch long by about one-eightieth of an inch in diameter, 
a truly microscopical instrument. On experimenting with 
♦Extract from the president's address before the American Microscop- 
ical Society, 1897. 
