lsi) '/'/,< American Geologist. September. is93 
Mr. McGee mentioned the great contrast of the old topo- 
graphic erosion forms of the early drift and the very uneven 
surface, with slight erosion or none, shown by the newer 
drift north of the moraines. 
Graphic Comparison of post-Columbia and post-Lafayettt 
Erosion. By W -I McGee. On a large area of the Atlantic 
coastal plain which has been very carefully studied about 
Washington, D. C, as illustrated by maps and sections, the 
average amount of erosion from the whole country is shown 
to have been 200 to 300 feet since the deposition of the La- 
fayette formation; but since the Columbia epoch the average 
erosion is perhaps no more than one foot from the same area. 
The difference in age of these formations is very great, and 
they are separated by an unconformity, due to this erosion, 
which is more important than any other similar horizon in 
the sequence of the Neocene and Pleistocene formations of 
this coastal belt. After the marine submergence to which 
the author attributes the Lafayette beds, the land is thought 
to have risen some 500 feet higher than now during its post- 
Lafayette denudation. 
An Illustration of the Effects of Stagnant Ice in Susses 
County, A". ./. By Prof. R. I). Salisbury, Chicago, 111. 
A Phase of Superficial Drift. By R. D. Salisbury. These 
two papers, owing to a temporary absence of the author, 
were read by title. 
Tertiary and Quaternary Stream Erosion of North America. 
By Warren Upham. If the accumulation of the Pleistocene 
continental ice-sheet was caused by a great epeirogenic up- 
lift and high plateau climate, as the author believes, excep- 
tional erosion by rivers during the late Tertiary and early 
Quaternary time should be found throughout the United 
States and Canada. The very remarkable erosion of the Col- 
orado canon and its tributaries, the extensive denudation of 
the Lafayette and older beds along the lower Mississippi and 
on the eastern coastal lowlands, the formation of the broad. 
flat valley of the Red river of the North, the channelling of 
the now submarine extension of the valleys of the Hudson 
and St. Lawrence rivers, of similar deeply submerged valleys 
on the coast of California, and of the fjords of our contin- 
ental borders thence northward to the Arctic archipelago and 
