TWENTY-NINTH ANNUAL MEETING. 1038 
the south. At the surface the surrounding ice becomes me!ted until the boulder 
stands on top of a taller-growing pedestal of ice. * 
An ice-field covering most of Iowa, northern Missouri, northeastern Kansas, 
and eastern Nebraska would be thinnest at its edges, whatever that thickness 
might be. It would be thickest along its middle line, and increase in height to 
the north until the snow-field was reached. The rate of ascent on a level plain 
has been estimated by various observers at 25 to 75 feet to the mile. The ascent 
should be most rapid from the south, by reason of the more rapid melting and 
the greater pitch of the earth’s surface in that direction. 
A field of ice that is spread over a plain should have the smoothest surface of 
any form of glacier. Rain or melted ice would simply run off, seeking the shortest 
cut to the ground. No need to account for interglacial streams or vast crevasses. 
While most likely the margin was deeply cut everywhere by water running down, 
the upper portions of the field must have been comparatively smooth and solid. 
It should resemble the remarkable Fan glacier of Redcliff, pictured and de- 
scribed by Professor Chamberlin in Journal of Geology, Vol. III, No. 4, p. 470, 
only on a vastly grander scale and sloping downward much less rapidly. But 
the slope should be continuous, and constantly increasing as the edge of the field 
was approached. 
When our field reached its greatest southern extent and began to retreat, 
the weather of July must have been hotter and moister than at present because 
of contiguity of the earth to the sun and of the Gulf of Mexico to the ice. A 
hot south wind blowing for three days as at present should remain above the 
freezing point for several hundred miles over the field of ice. Is it too much to 
say the surface of the ice would melt for 500 miles north of Kansas City? The 
ice would be melted by rainfall as well as by sunshine. A southwest wind would 
bring as much heat and much less moisture. In either case the surface would 
melt except where protected by the large boulders, whose pedestals were still 
growing taller. 
If we allow that the slope of surface toward the south was 25 feet to the mile, 
the ice 100 miles to the north of here should be 2,500 feet in thickness and 
greater still further north. 
A GRanp Coast. 
A hot day comes. Many warm days have preceded it. A boulder weighing 
100 tons stands on a high pedestal 100 miles north of Topeka. The south wind 
blows. The boulder is undermined on the south side. The column breaks and 
the boulder is forcefully flung to the floor of ice. The ice is nearly level, but it 
descends gently to the south. The boulder has momentum enough in its fall to 
start it sliding to the south. The ice issmooth and solid. What is there to stop 
the boulder? Does it strike the icy pedestal of another boulder? Let it glance 
off, and with a graceful curve resume its course. The descent increases slightly. 
The momentum increases. The velocity increases greatly. Soon the force and 
speed becomes tremendous. It rivals a railroad train. It surpasses the pneu- 
matic dispatch. One hundred miles an hour. Give it an hour, it ought to reach 
its destination. 
The ice over which it slides is growing dirty and hummocky. The friction is 
insufficient to stop the boulder. The dirt polishes the stone. The hummocks 
fly before it. A train of smaller stones follow behind it. Who shall estimate 
the heat developed in the boulder during its rapid transit? 
* See 13th Ann. Rep. U. S. G.S., Part II, p. 70, second expedition to Mt. St. Elias, by Israel 
C. Russell; surface features of the Malaspina glacier, 
