Davis.] 
352 
[January 18 , 
Mention may here be made of the small ponds held upon the 
ice surface where two glaciers meet, because they are higher in 
the middle than at the sides. The ponds are but a few hundred 
feet across, and very shallow ; their position is permanent but not 
their volume ; in winter they are probably frozen solid, but in 
summer have an open water surface. Examples may be found 
on the Mer de Glace at the junction of the glaciers de Tacul and 
de Lechaud; on the glacier de Talefre just below the Jardin; on 
the Gorner glacier, below Monte Rosa, and elsewhere . 1 The 
lakes described as occurring on the great glaciers of the Himalaya 
are probably of this kind . 2 
Lakes of the third division of this species are unknown at pres- 
ent because the conditions which produced them have passed 
away; but during the glacial period, when Northeastern Amer- 
ica and Northwestern Europe were covered by vast sheets 
of ice, they must have been of common occurrence in every val- 
ley that sloped against the retreating ice front; and as having 
had a strong influence on the existing topography of our country, 
they merit attention, though only affairs of the past. 
The headwaters of the Red River of the North are marked on 
the east and west by a series of low, irregular drift-mounds, that 
were formed as a terminal moraine of a lobe of the great glacier 
during a halt in its melting away. When the retreat was resumed, 
the space gradually left between the moraine and the ice front 
was filled with water from the melting, and as the present escape 
to the north was prevented, the lake rose until it overflowed a 
low gap at the south and ran down into the Minnesota. 
After a sufficient retreat of the ice, the lake was drained north- 
ward, and left a plain of remarkably level surface, made of the 
fine detritus that had been washed into it. It is important to 
note that the old channel of discharge, even close to the outlet, 
is a broad, deep trough cut in the drift, and of a size proportionate 
to the overflow of a large lake, while its present occupant, the 
Minnesota, is but a small stream at its headwaters, quite lost in 
the great valley of its predecessor. The old lake has been well 
named Lake Agassiz : Lake Winnipeg is probably connected with 
1 L. Agassiz, Etudes sur les Glaciers, 220. 
2 Godwin-Austen. Roy. Geogr. Soc. Journ., xxxiv, 1864, 19. 
