A72 M.S. W. JEFFERSON 
g. East valley ice melts leaving modern topography. 
10. The trenching river finds the rocks and cuts its gorge 
with present falls and rapids. 
Ponds, such as those here described should be fairly numer- 
ous in glaciated regions. The kettle ponds are of course widely 
observed. ~ 
Pools of abandoned falls of glacial origin are not often cited. 
A superb example is noted by I. C. Russell’ at the foot of a 400- 
foot basaltic cliff near Coulée City, Washington, over which the 
waters of the Columbia plunged when an ice dam drove them 
through the fault chasm of the Grand Coulée (p. 91). Another 
such pool is Thaxter Lake near Taylor’s Falls, Minnesota, 
excavated by the tumbling waters of the deviated St. Croix.’ 
Other fine examples are the Green Lakes at Jamesville and 
other points near Syracuse, reported by Gilbert and lately 
described by Quereau3 Here magnificent glacial outlets of 
Lake Iroquois, paralleling the Mohawk outlet, but farther 
south, cut broad trenches across the promontories of the ragged 
escarpment south of Syracuse and plunged Niagara-like into 
great basins below. The trenches are now dry high in the hills, 
but the basins are filled with placid greenish waters. 
M.S. W. JEFFERSON. 
™ Bull. 108, U. S. Geol. Surv. 
2 Berkey, Am. Geol. Dec. 1897, p. 352. 
3 Bull. Geol. Soc. Am., Feb. 1808. 
