ed ia 
: Je now well known. 
the ice-sheet must evidently have become considerably attenuated 
’ Missouri with all its tributaries on the right down into Kansas, 
2 The Ancient Glaciers of the Rocky Mountains. (January, 
in the Wisconsin region, though still retaining momentum suffi- 
cient to carry it down the Mississippi valley into Missouri and 
Kansas. In Dr. Aughey’s recent interesting volume on Nebraska, 
the extension of the ice westward into that State is clearly proved, 
and the ice-movement is there shown to have taken a south- 
south-east direction, or down the Missouri valley. No doubt the 
glacier had thinned away greatly in that region. Its south-western 
and western margin, however, remains to be traced up the plains 
watered by the Missouri. And the day is probably not far dis- 
tant when the work so well done by Mr. Dawson, in British 
Columbia, will be prolonged into the Missouri region, and the 
precise limits and course of the ice-sheet will be mapped across the 
whole breadth of the continent. 
Subsequent explorations have amply confirmed the original 
observation of Prof. Whitney as to the driftless nature of the sur- 
face of the vast interior region lying between the Missouri valley 
and the Sierra Nevada. The fact may seem almost incredible _ 
that the low ground of Eastern North America should have been 4 : 
buried under a southward-creeping ice-sheet, from which the _ 
lofty plateaux of the West remained free. The cause of this dif- : 
ference was probably meteorological, as Prof. Dana had pointed 
out, the snow-fall over the Rocky mountains and western ranges 
having been insufficient to give birth to a general ice-sheet — 
descending from those heights into the plains. But the question 
remains: what was the probable condition of the West during — 
the time when glaciation in the East was at its height? We must 
reaches the sea, was then blocked up with ice. The valley of the 
was under ice. Any water-drainage from the west would be 
allel with the ice and j join the streams, escaping from its melting 
end. Iam not aware, however, that any evidence of such arrest 
of drainage has yet been met with, though it is a point deserving 
of attention. 
That the mountain ranges of the West had their glaciers, is 
Even at the present time, as Mr. Clarence 
