128 IRRIGATION. 



the next level, and so on until all are covered. A sufficient 

 quantity of water is allowed to pass on to each level to 

 maintain the proper depth, and allow a gentle current to 

 flow from the drains. This is important when the tem- 

 perature falls below the freezing point. Observations 

 have been made, which have shown that when this has 

 occurred, and the temperature of the air has been as low 



Fig. 61. SPOUT IN THE BAKE. 



as 26, that of the grass beneath the ice has been no 

 lower than 42, and that vegetation was still active, as 

 shown by the color of the verdure. 



As regards the amount of water used, and the manner 

 of using it, the following experiences may be cited. 



A comparison of fields that have been less abundantly 

 watered, with those that have received a copious supply, 

 has shown that the crops upon the latter have been in- 

 fallibly increased. 



Where during one Winter the irrigation has been sus- 

 pended, the succeeding crop has been little or nothing. 



Where the water that has passed over a field has been 

 flowed upon another, the crop of the latter has been very 

 inferior to that of the former, showing conclusively that 

 the earth had completely abstracted the fertilizing proper- 

 ty of the water in its first contact with it. 



In proportion to the abundance of water supplied dur- 

 ing the Winter, so is the yield of grass in the Summer. 

 In short, facts are conclusive to show that the quantity 

 of water that can be used, is the gauge of the harvest to be 

 expected. The Winter irrigation supplies the fertility, that 

 of the Summer simply supplies the necessary moisture. 

 In this respect the action of water constantly passing in a 



