358 The American Geologist. May, 1892 
Summaries of the work of this survey, and of the present state of 
knowledge of North American geologic systems, with correlation of 
formations throughout the country, were in progress of preparation, as 
follows: on the Pleistocene, by T. C. Chamberlin ; Neocene, William H. 
Dall; Eocene, W. B. Clark ; Cretaceous (including the Laramie ), C. A. 
White ; Jura-Trias, I. C. Russell; Carboniferous and Devonian, H. 8. 
Williams; Silurian and Cambrian, C. D. Walcott; Algonkian and 
Archean, C. R. Van Hise ; correlation by vertebrate paleontology, O. C. 
Marsh ; correlation by pal:eobotany, Lester F. Ward ; resumé of North 
American stratigraphy, W. J. McGee; and discussion of principles of 
correlation, G. K. Gilbert. Three of these memoirs, by White, Williams, 
and Walcott, have been siuce issued as bulletins of the survey. 
Professor Pumpelly’s report of the progress of his investigation of the 
structure of the Green mountains shows that they consist of compressed ° 
folds overturned toward the west. The cores of the folds are pre- 
Cambrian crystalline rocks, which are generally hidden. Metamor- 
phosed detrital rocks form the surface, apparently comprising the entire 
Cambriam system and the Silurian upward to the Hudson River forma- 
tion. 
In the work of the Atlantic Coast division, under the direction of 
Prof. N.S. Shaler, the morasses and superficial deposits of Massachu- 
setts have been mapped, and are found to exhibit a gradual decrease 
of stratified gravel, sand and clay, and an increase of the areas of till, in 
proceeding from the seaboard inland to the western and higher part tof 
the state; moraines have been discovered in the interior, far back from 
the great terminal moraine which forms the crest of Long Island, and 
the drumlins are found to display diverse degrees of development, the 
least prominent grading insensibly into ordinary sheet till. 
The structure and origin of the Appalachian mountains have been 
studied by Mr. G. IK. Gilbert, and Mr, Bailey Willis, and the latter has 
undertaken a series of experiments to represent in miniature the folds 
of these mountains by subjecting layers of plastic material to lateral 
thrust. 
Exploration of the rock formations surrounding lake Superior, by 
Prof. C. R. Van Hise, has been extended over a large area, in north- 
eastern Minnesota and northern Wisconsin and Michigan. For the 
extensive series of rocks, supposed to be beneath the Cambrian and 
above the Archiean, well developed in this district, the name Algonkian 
is proposed, This is another addition to the synonymy of the already 
burdensome and complicated nomenclature of this uncertain horizon in 
the geological scale. 
In the Glacial division, under the direction of Pres. T. C. Cham- 
berlin, work has related tothe glacial Lake Agassiz ; to the terminal 
moraines, and the succession of deposits which make up the general 
drift sheet: the gravels and sands of glacial origin continuing beyond 
the limit of the ice incursions in the basin of the Mississipi; trains of 
boulders in Wisconsin ; and the osars, kames, and valley drift in Maine. 
Reports on most of these subjects are nearly ready for publication. 
