CORRECT ESTIMATES OP WATER NEEDED. 23 



is far beyond the capacity of any artesian well to supply, 

 unless it be one of extraordinary volume. 



It is very important that the quantity of water needed 

 for irrigation should be accurately estimated. A mistake 

 in an estimate may lead to the construction of inadequate 

 works, and the useless expenditure of much money. 

 Estimates generally err upon the side of insufficiency 

 rather than otherwise, and much error has been spread 

 abroad by persons and journals having considerable in- 

 fluence. Not long ago the " Scientific American " edi- 

 torially announced that one artesian well would supply a 

 farm of 640 acres upon the plains with water for irriga- 

 tion, and would also form a nucleus for many large stock 

 farms." The late Horace Greeley, who, although an en- 

 thusiast upon this subject, was more nearly correct, 

 thought one artesian well would serve to irrigate a quarter 

 section of land, or 160 acres. The wildly excessive esti- 

 mates of the value of a certain amount of water might 

 be easily disproved by the careful use of a few figures, 

 and a little common sense. For instance, let any person 

 who has ever watered a garden plot and who knows the 

 effect of one inch in depth of water upon a dry soil, con- 

 sider the following facts, and then apply them to the mat- 

 ter in question, and he will readily see the absurdity of 

 the estimates above referred to. 



1st. There are 6,272,640 square inches in an acre. 



2d. One inch of water, or a stream one inch wide and 

 deep, flowing 4 miles an hour, will equal 6,082,560 inches 

 in 24 hours. 



3rd. Therefore 1 inch of water flowing 4 miles an hour, 

 for 24 hours, will cover one acre nearly an inch deep. 



4h. One inch of water per week equals 52 inches per 

 year, or more than the yearly rain-fall. 



6th. Therefore 1 inch of water should serve to irrigate 

 only 7 acres once a week, at least as well as the average 

 rain-fall. 



