106 IRRIGATION. 



By this contrivance a very small spring may be utilized. 

 One yielding 2 quarts per second will serve to water four 

 acres of meadow if stored for 24 hours, and discharged 

 periodically at intervals of that length of time. During 

 this period 43,200 gallons would be accumulated, which 

 would supply nearly one quart of water to every square foot 

 upon the four 'acres ; a very ample allowance in addition 

 to what is furnished by the rainfall, to secure a full crop 

 of grass. It would be preferable to accumulate a larger 

 quantity of water than this, if possible, and to give a 

 more copious watering less frequently. A thorough satu- 

 ration of the soil at intervals, as has been before explained, 

 is better than more moderate waterings more frequently 

 given. Air is as vital a necessity to vegetation as water, 

 and if access of air is denied, the roots of the plants 

 must perish. Where water goes, air follows, and as evap- 

 oration takes place, air fills the space previously occupied 

 by the water. To moisten the soil to a depth of several 

 inches gives that coolness which the grass roots find neces- 

 sary for their healthful growth; but to moisten the soil to 

 a depth of only an inch or two, gives no supply sufficient 

 to resist the drying effects of the sun's heat, or a hot dry 

 summer breeze. Two inches of water given every week 

 would be a very good supply, and with a spring of the 

 size of flow mentioned, economically stored, twelve acres 

 of grass could be watered once a week. The effect would 

 be equivalent to that of the fall of a steady, moderate 

 shower during a whole day and night, and occurring every 

 week, and every farmer can readily understand the value 

 of such a shower upon his meadows. 



To store 43,200 gallons of water will require a reservoir 

 of 5,760 cubic feet. One 40 by 20 feet, and 7 feet deep, 

 will have about this capacity. If the width is doubled, 

 the depth may be decreased one half. The shallower it 

 it can be made the better for many reasons. The temper- 

 ature of spring water is generally too low in the Summer 



