322 EEPOET UNITED STATES GEOLOGICAL SUEVEY. 



of the irrigating season. Moreover, to obtain «i result from -which it 

 would be safe to draw definite conclusions, the season should have been 

 a dry one (for it is with the minimum supply of raiu that we have to 

 deal), and the normal regimen of the streams should not have been 

 recently disturbed by rains. In our work, it is not possible to choose 

 the time and conditions for making these measurements; but such 

 measurements as we have made and collected will serve to give a rough 

 approximation to the irrigating power of all the principal streams. 



