IOWA ACADEMY OP SCIENCES. 93 



the relative dates of the Kansan, Illinoian, lowan 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 F. M. WITTER. 



In the year 1873, a division of geologists under the manage- 

 ment of Dr. F. 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 Ear 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 



