Irrigation. 257 



the warm, growing months of May, June, July, August and September, most vegeta- 

 tion requires an inch in depth over the entire surface of the land every five days. 

 This is, of course, only an average. This quantity, estimated as needed by our 

 gardens, would be equivalent to six inches per month of rain-fall. If we compare 

 this amount with the actual rain-fall, we shall arrive at an idea of what is to be 

 supplied artificially. 



"The rain-fall at Boston for the past six years (to 1878), for the five growing 

 months named, varies from a maximum of 10^ inches, in August, 1872, to a mini- 

 mum of 0.65 inch, in June, 1873. During these six years there was not a single 

 season when we did not suffer more or less from drought during some portion of the 

 summer. Twenty-one of the thirty months in question had less rain-fall than six 

 inches per month, and the average of these twenty-one months was about 3.02 inches 

 per month, or only about half of what was needed. Some of the protracted seasons 

 of drought were almost entirely rainless for six weeks, during which the weather 

 was excessively hot and windy, and vegetation suffered extremely in consequence." 



Mr. Philbrick estimates that 27,000 gallons, or 108 tons, of water are 

 needed per acre at each watering, which, in a dry period, should be 

 repeated every five days. This enormous quantity leads him to suggest 

 that " before embarking in an enterprise of irrigation, it would be best to 

 make sure that the source can be depended upon for a sufficient supply of 

 water in the driest seasons ; for, it is precisely at such times that the most 

 water is needed. Ordinary springs and wells, therefore, are entirely inade- 

 quate to furnish water for anything more than a small patch or garden. 

 The only sources to be depended upon for large areas are unfailing 

 streams, lakes and ponds. There are few gardens so favorably situated 

 that the water can be drawn from canals and ditches directly from some 

 pond or stream. When this can be done, it is by far the cheapest 

 method ; and it is in this way that the extensive irrigating works of Lom- 

 bardy, Spain, France, California, and Colorado are constructed. Where 

 this system is adopted, considerable expense is required to grade the land 

 into inclined beds, so as to distribute the water easily and evenly ; but, 

 once done, the water is applied at a very trifling cost so cheaply that it 

 is used for farm crops in Lombardy and the South of France." 



In most instances, however, our land is so located that we cannot 

 irrigate it by a natural flow and fall of water. In this case, it may be 

 distributed by water-carts and by hand. This can be done only on a very 

 small scale. The cost in time and labor would be much too great for 

 profitable returns, and the ground would be so beaten and trampled as to 

 cause much injury. Such methods may answer very well for small and 

 well-mulched fruit gardens, making the home supply certain and large, 

 but it is inadequate from a business point of view. Distributing water 

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