IOWA ACADEMY OF SCIENCES. 
93 
the relative dates of the Kansan, Illinoian, Iowan and Wiscon- 
sin glaciations. But on this question scarcely more than a 
very rude approximation is likely to be reached. As indicated 
above, the work involved in filling is especially difficult to 
determine. These difficulties, however, are no greater than 
those involved in the estimates of the changes of drainage 
area which the Mississippi has experienced. The object of 
the present paper is accomplished if the complexity of the 
history has been adequately presented. The chronological 
determinations must be deferred to a time when more refined 
methods of investigation are instituted than are now at com- 
mand. 
OBSERVATIONS ON THE GEOLOGY OF STEAM- 
BOAT SPRINGS, COLORADO. 
BY P. M. WITTER. 
In the year 1873, a division of geologists under the mauage- 
ment of Dr. P. V. Hayden, made a survey of the region from 
Willow Creek pass, between North and Middle Parks, across 
the park range down the Yuma or Bear river to the White 
river, around to Eagle river and up the Grand, of which Wil- 
low creek, in Middle Park, is a tributary. In this report, very 
brief mention is made of Steamboat Springs, although the 
trail on their map does not pass nearer than twenty-five or 
thirty miles to the Springs. 
Steamboat Springs is now not far from 100 miles by wagon 
road from a railway. Rawlins, on the Union Pacific in Wyo- 
ming, is probably the nearest railroad point on the north, and 
Glenwood Springs, on the Denver & Rio Grande, is the nearest 
on the south. Last July our party left North Park in its 
extreme southwest corner at Rabbit Bar peak. This mountain 
IS the most conspicuous in the park range, immediately west 
of North Park. Prom near Pinkhampton, in the northeast 
corner of North Park, Rabbit Ear is plainly visible, a distance 
of sixty miles or more. This peak is capped by two immense 
vertical rocks about 100 feet apart. These rocks have sug- 
gested the name for the peak. By means of a spruce-tree 
ladder we climbed to the top of one of these huge “ears. ” We 
