GENERAL MEETING. 33 
titled ““ Abstract of a Report on the Geology of Leadville,” in the 
Second Annual Report of the Director of the United States Geo- 
logical Survey. 
While the speaker’s studies have thus far been mainly confined to 
limestone deposits, he has reason to believe that essentially the same 
process has produced a large proportion of ore deposits in crystal- 
line and eruptive rocks, and that to the class of metamorphic de- 
posits belong most of the so-called fissure veins of the Rocky Moun- 
tain region. That is, that they are not the filling in of pre-existent 
open fissures by vein materials foreign to the adjoining rocks, but 
simply a metamorphic change of these rocks themselves along 
channels of easy access to percolating waters; and according to the 
character of the material held in solution by these waters, these 
rocks have been more or less changed into quartz and metallic min- 
erals, to a greater or less width, as the case may be. Numerous 
instances of such veins will be found in the forthcoming Census 
Report upon the Statistics and Technology of the Precious Metals, 
by Mr. G. F. Becker and the speaker. 
234TH MEETING. Aprit 21, 1883. 
Vice-President Britiincs in the Chair. 
Forty members present. 
The Chair announced that Messrs. WASHINGTON CARRUTHERS 
Kerr and SAMUEL FRANKLIN Emmons had been elected members. 
Mr. W. H. Datu addressed the Society on 
GLACIATION IN ALASKA, 
illustrating his remarks by maps of the territory and of the glacial 
areas of the St. Elias Alps and Kachekmak Bay, Cook’s Inlet, the 
latter being from surveys made by him under the direction of the 
U.S. Coast Survey. 
He called attention in the first place to the wide differences in 
the character of the masses of ice resulting from the consolidation 
of snow by gravity (which would usually be classed as glaciers), 
as observed by him during nine years’ exploration in Alaska. 
These might be classed under several heads: as plateau-ice, filling 
