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1876.] Explorations in Colorado. 161 
At 10.45 she came to cup 3, and I went to bed. At seven 
o'clock the next morning the larve were all removed. In watch- 
ing this ant I was much struck by the difficulty she seemed to 
experience in finding her way. She wandered about at times 
most irresolutely, and, instead of coming straight across from the 
door of the frame to the cups, kept along the side of the box; 
so that in coming to cup 3 she went twice as far as she need have 
done. Again, it is remarkable that she should have kept on vis- 
iting the empty cups time after time. I watched for this ant 
carefully on the following day ; but she did not come out at all. 
During the time she was under observation, from 1 till 10.45, 
though there were always ants roaming about, few climbed up 
the walls of the cups. Five found their way into the (empty) 
cup 1 and one only to cup 3. It is clear, therefore, that the ant 
under observation did not communicate her discovery of larvæ to 
her friends, 
EXPLORATIONS IN COLORADO UNDER PROFESSOR 
HAYDEN IN 1875. 
THE United States Geological and Geographical Survey of the 
Territories, under the direction of Professor Hayden, during 
the season of 1875, continued the work of the two previous sea- 
‘Sons in Colorado, completing the southern and southwestern por- 
tions, including a belt fifteen miles in width of Northern New 
Mexico and Eastern Utah. 
The entire force was divided into seven parties. The district 
_ Strveyed by the first party, under A. D. Wilson, embraced an 
area of 12,400 square miles. It contains the foot-hills sloping 
eastward from the Front Range, the southern continuation of 
the Saugre de Christo Range, the southern end of the San Luis 
ey, the extension of the La Plata Mountains, and the lower 
country of the Rio San Juan and its tributaries. A small por- 
tion of the sedimentary eastern foot-hills was first surveyed, and 
the work was then carried westward to the mountainous vicinity 
of the upper Rio Grande. Instead of forming a well-defined, 
ly-limited range, the mountains south of the Rio Grande are 
formed by a high plateau with numerous isolated peaks. Both the 
Plateau and the peaks mentioned are volcanic, showing the char- 
acteristic regularity of flows prevalent there. From the position 
*t volcanic beds composing the higher peaks it may be inferred 
tat one time the summit of the plateau extended to a consid- 
OL, X. — xo. 3, 11 
