272 , The American Geologist. October, 1893 
The Pre-Paleozoic Floor in the Northwestern States. Prof. C. W. 
II m.l, University of Minnesota. (Absent; read by title.) 
Distribution of Pre-Cambrian Volcanic Rocks along the Eastern Bor- 
der of the United States and Canada. Prof. George H. Williams, 
Johns Hopkins University. 
After the rending of these papers they were briefly discussed 
by Mr. C. D. Walcott, Prof. H. S. Williams, Dr. Sklwyn, Mr. 
Ami, and others. 
A special discussion, by Profs. JoSEPB Le ( onte, II. S. Wil- 
liams, and others, was then taken up, on the question : Are 
there any Natural Geological Divisions of World-wide Extent? 
Professor Le Conte spoke affirmatively, citing as one of these 
divisions the Quaternary or Psychozoic era. This has been 
characterized by ice-sheets in northern and southern temper- 
ate latitudes; by the appearance of man, whence the era re- 
ceives its name referring to its place in the ascending scale of 
life; and by great epeirogenic movements, as the uplift of the 
Sierra Nevada probably 10,000 feet above its former night, 
and the overthrusting and upheaval of the St. Elias range, 
besides probably equally grand changes in portions of the Alp- 
Ilimalayan mountain belt. The world-wide, or certainly very 
extensive, epeirogenic and climatic disturbances of this era, 
the latter probably resulting from the former, and great 
changes of the mammalian faunas, especially the advent of 
man, mark this as a distinct and world-wide geologic time di- 
vision. In earlier times, the next preceding similarly impor- 
tant and general faunal changes, likewise attended and 
doubtless chiefly caused by great earth movements of continent 
and mountain building, were at the end of the Cretaceous 
period, and far earlier at the close of the Carboniferous and 
Permian ages. By these three stages of exceptionally rapid 
and general extinction of old and evolution of new species, 
the history of life on the earth is naturally divided into the 
Paleozoic, Mesozoic, Cenozoic, and Psychozoic eras. 
On Friday Prof. Joseph Le Conte and Mr. Hjalmar Lundbohm 
presided, and the program comprised the following eleven 
papers : 
Huronian versus Algonkian. Dr. A. R. C. Selwyn, Geological Sur- 
vey of Canada. 
On the Migration of Material during the Metamorphism of Rock 
Masses. Alfred Harker, St. John's College, Cambridge, England. 
(Absent ; read by Mr. Arthur Winslow.) 
Wave-like Progress of an Epeirogenic Uplift. Warren Upham, Geo- 
logical Survey of Minnesota. 
Eruptive Phenomena of Brazil. Dr. O. A. Derby, Geological Sur- 
vey of Sao Paulo. (Absent; read by title.) 
Zur Nereitea Frage. Dr. H. B. Geinitz, Dresden. (Absent; read by 
title.) 
Genetic Classification of Geology. W J McGee, Bureau of Eth- 
nology. 
Precious Stones and their Geological Occurrence. Dr. Geo. F. 
Kunz. (Absent; read by title.) 
