WATER SUPPLY. 71 
causes until the entire subject is mastered. The simpler and more imme- 
diate meteoric reactions have been so far analyzed that their results are 
daily predicted ; but the remote sources of our daily changes, as well as the 
causes of the greater cycles of change, are still beyond our reach. Although 
withdrawn from the domain of the unknowable, they remain within that of 
the unknown. 
THEORY OF HUMAN AGENCIES. 
The only remaining theory of value is the one advocated by Pro- 
fessor Powell: that the phenomena are to be ascribed to the modifica- 
tion of the surface of the earth by the agency of man. The rise of the 
lake and the increase of streams have been observed since the settlement of 
the country by the white man, and the sage brush on the old storm line 
shows that they had not been carried to the same extent at any previous 
period in the century. They have coincided in time with the extension of 
the operations of civilization; and the settlers attach this idea to the facts 
in detail as well as in general. They have frequently told me that 
wherever and whenever a settlement was established, there followed in a 
few years an increase of the water supply, and these statements have been 
supported by such enumerations of details that they seem worthy of consid- 
eration. If they are well founded, the secret of the change will surely be 
found among the modifications incident to the operations of the settler. 
Similar testimony was gathered by Prof. Cyrus Thomas in 1869 in 
regard to the increase of water supply at the western edge of the plains, 
and the following conclusion appears in his report to Dr. Hayden (page 
237 of the reprint of Dr. Hayden’s reports for 1867, 1868, and 1869): 
All this, it seems to me, must lead to the conclusion that since the territory [Colorado] has begun 
to be settled, towns and cities built up, farms cultivated, mines opened, and roads made and travelled, 
there has been a gradual increase of moisture. Be the cause what it may, unless it is assumed that 
there is a cycle of years through which there is an increase, and that there will be a corresponding 
decrease, the fact must be admitted upon this accumulated testimony. I therefore give it as my firm 
conviction that this increase is of a permanent nature, and not periodical, and that it has commenced 
within eight years past, and that it is in some way connected with the settlement of the country, and 
that as the population increases the moisture will increase. 
Notwithstanding the confidence of Professor Thomas’s conclusions, he 
appears to have reached them by a leap, for he makes no attempt to analyze 
the influence of civilized man on nature to which he appeals. Before we 
