INCORRECT IDEAS. 251 



any great river to supply it ? The absurdity of the above 

 assertion is manifest. 



Again, this seems a proper place to refer to the erro- 

 neous figuring, noticed on page 172, in regard to the 

 canals in California. A canal 55 feet wide, upon the sur- 

 face, (and averaging only 50 feet in width), 4 feet deep, 

 and flowing 2 miles an hour, can only supply 600 cubic 

 feet per second, or enough to give one cubic foot per 100 

 acres to 60,000 acres, or half a cubic foot, per 100 acres, 

 to 120,000 acres ; instead of supplying 325, 000 acres the 

 capacity claimed for it. But 25 per cent of the supply 

 may easily be lost on the route, and this would serve to 

 still further reduce the number of acres served. It is 

 very important that these calculations should be made 

 with exactness, or some very costly mistakes may be made, 

 which may very reasonably tend to disgust persons who 

 are not well informed, as to the actual cost and merits of 

 irrigation. 



The manner of construction of lesser canals, for dis- 

 tributing the water, should be consistent in all respects 

 with the conditions and requirements here pointed out ; 

 there is probably no necessity to enter into details which 

 might be tedious, and would necessarily be a repetition, 

 to some extent, of what has been described heretofore. 



One point, however, must not be omitted ; that is the 

 connections of the earth works with flumes, gate frames, 

 sluices and boxes for the proper conducting of the water 

 into devious courses. It is a known property of water 

 that it is very much inclined to " creep " along the sur- 

 face of any pipe, arch, culvert or sluice, whether of iron, 

 brick, masonry, or wood, which is imbedded in earth 

 work. The connections should, therefore, be made with 

 great care. As a rule, the walls of gateways, or sluices, 

 should be protected with flanking walls of the same 

 material of which the main works are constructed, or 

 else should be protected by piles driven firmly into the 



