130 IRRIGATION. 



upon it, if desired, by closing the outlet at the foot ; or 

 the outlet may be opened only so much as to allow a 

 gentle current to pass over the meadow and maintaining 

 the water at its stated depth. Upon level meadows less 

 water may be used than upon meadows having consider- 

 able slope. The more water that can be made to pass 

 over the grass, the better, up to the point of the satura- 

 tion of the soil. The quantity of water that may be used 

 depends upon the inclination of the surface and the qual- 

 ity of the soil. 



Where the surface is perfectly level, and of a clayey 

 character, the minimum quantity of water can be used. 

 When the surface slopes so as to reach the extreme in- 

 clination practicable for these meadows, and the soil is 

 gravelly, sandy, and porous, with a porous subsoil, then 

 the maximum quantity of water can be used. 



An instance is stated by M. Herve Mangon, in his work 

 already referred to, of the irrigation of meadows in the 

 valleys of the Vosges, Eastern France, in which water is 

 employed to such an extraordinary extent that the total 

 quantity used in a year would cover the soil to a depth of 

 thirteen hundred feet. In another case the quantity of 

 water used between the end of November and the middle 

 of August following, was equal to a total depth of 27 feet. 

 The whole of this time was divided into eight periods of 

 watering. But the locality in which these extreme cases 

 occurred, is one where the meadows are rarely level, and 

 have generally an extreme inclination ; the soil is gravelly, 

 being derived from the schistose rocks of the surrounding 

 hills, and is very porous and loose in texture, and the 

 water of the streams is highly charged with sediment and 

 soluble matter, from the decomposed rocks. At least 

 such is the case in the valley of Waldersbach, a locality 

 much visited by travelers on account of its connection 

 with the history of the renowned Father Oberlin, and 

 where the author has seen the grassy hill sides flowed 



