THE IRRIGATION AGE. 229 



less than a quarter of a mile in any direction to the rim of the water- 

 shed from which you can readily see they must come. It is much the 

 same and often worse with water passing through soil and even 

 through pure sand it is provokingly slow. No one can calculate its 

 rate of progress but you can generally rely upon its being provok- 

 ingly slow when you need much water. If it were otherwise few oi 

 our water supplies would hold out after one dry year. People love to 

 flatter themselves that the water comes from some distant source, 

 independent of the watershed about the well. If in a well defined 

 gravel channel this is generally the case and most wells in such for- 

 mation are reliable under very heavy draft. But if in soil, or decayed 

 rock the presumption is heavily the other way and even sand is 

 often a mere sponge for a local watershed. Even where it is certain 

 that it is not I have found the passage of water through it so slow 

 that a well twenty feet across pumped down from eight feet to two 

 feet took one hour to regain one foot with the water standing at the 

 eight foot level all around it. This was a foot an hour under an 

 average pressure of five and one-half feet. No one can sav what it 

 would have been under no pressure but with the grade of the stream 

 twenty-five feet to the mile. 



A mile and two thirds a year is quite slow under a pressure of 

 five and a half feet. 



EVEN FOR FINE QUICKSAND WHICH THIS WAS. 



Yet I measured and timed this well myself as soon as the pump 

 stopped and could not have made more than five percent, error at the 

 most. Through most sand water will pass more rapidly under that 

 head yet you are liable at any time to be greatly disappointed in its 

 velocity. Wells in soil, soft rock, and fine sand will do for a. light 

 supply and also to help out in bad seasons but should not be made a 

 basis of farther expansion in planting until time has proved what they 

 will do. The only danger in the present great developing movement is 

 the cry Eureka. Too many may think they have solved the great 

 problem only to find that what may be valuable as a reserve will not 

 stand the brunt of steady battle. 



Strange sa it may seem a gravel channel in which the water 

 does not rise in the pipe 



MAY BE A MORE RELIABLE SOURCE OF SUPPLY 



than one where it does. Where pressure is indicated by the rising of 

 the water above the top of the stratum in which it is struck it means 

 resistance all the way back to the last thread of water that feeds it 

 below ground. If this resistance be removed by opening the channel 

 by wells and drawing out the resisting water the supply is quite apt 

 to come in much faster than when the resistance of the water below 

 aided friction in holding it back. Consequently too many taps on an 

 artesian belt may seriously reduce it by accelerating the feed of water 



