172 The American Geologist. septombor,i898 
insignificant drainage of the Erie basin. This argues for greater 
length of postglacial time. On the other hand there is a ques- 
tion as to the origin of the gorge, whether cut dc novo, or in 
part reexcavated or enlarged by the modern river. The chief 
students of the subject have been Gilbert, Spencer, Upham 
and Taylor. Out of the mass of literature two papers must be 
noticed: that of Gilbert, "The History of Niagara River," 
1890, which placed the elements of the problem before the 
public; and the paper by F. B. Taylor, 1898, "Origin of the 
Gorge of the Whirlpool Rapids at Niagara," which gives the 
latest results of the correlation study of Niagara and the glacial 
lakes. 
The recession of St. Anthony's Falls in the Mississippi has 
also been studied as a measuring rod of postglacial time, espe- 
cially by N. H. Winchell, with results concordant with those 
of Niagara and other similar studies. 
Recently Mr. H. M. Bannister has argued for great dura- 
tion of the ice sheet, from data derived from transportation of 
far-travelled erratics; and Mr. Taylor finds a great length of 
time required to form the moraines of recession in the Erie- 
Huron basin laid down by the slow oscillations of the ice front; 
the latter paper favoring astronomical forces as a cause of gla- 
ciation, at least in part. 
The question of glacial time is closely connected with the 
problem of glacial cause. 
INTERPRETATION OF SPECIAL PHENOMENA. 
Drumlins. — These are usually conspicuous topographic 
features and frequent references to them, under various de- 
scriptive terms, occur in the early literature of the drift. Un- 
der the diluvial hypothesis little effort was made to explain 
their origin, and Edward Hitchcock found in them an objec- 
tion to the glacial theory. 
The name "drumlm" was applied in 1866 to similar drift 
masses in Ireland by H. M. Close. In America various ap- 
pellations were given: by professor Shaler, who was the first 
American to write upon them, — "drums" and "sow-backs," 
1870; by C. H. Hitchcock, "lenticular hills," 1876. The elon- 
gated forms of central New York were described in 1882 by 
Laurence Johnson as "parallel drift hills," and professor 
