112 



IRRIGATION. 



the dam is seen at fig. 44 ; the hight of which is 8 feet, 

 width 16 feet, and the puddled clay wall in the center is 

 shown by the darkly shaded portion. Where the spring 

 is of sufficient volume to supply all the water that may 

 be needed, it would still be worth while to provide the 

 reservoir for the sake of gaining the increased tempera 

 ture ; but in such cases the reservoir will not be needed 

 for the purpose of distribution, but only to warm the 



Fig. 47. MANNER OF COLLECTING THE WATER OF SPRINGS. 



water. The overflow, then, only will be used, which 

 will escape on the same level as that of the inlet. The 

 course of the current through the reservoir should be 

 made as circuitous as possible by means of a division 

 of boards in the center, that the exposure of the cold 

 water to the warm air or sun s heat may be the longer. 

 When water is retained solely for this purpose, the space 

 in which it is confined should be large and shallow, so 

 that the exposure of the water to the sun s heat, and the 



