MAT. 317 



watered. The return to the ditch at the other 

 end of the field, and letting down the stops, 42 

 and 43, it is evident that the water will flow into 

 the trench 34, and tiie stop, 44, being down, the 

 pane, 15, is watered, and the trench, 45, becomes 

 a drain, which, successively, conducts the water, as 

 above explained, over the panes 16, 17, 18 and 

 19. Now it is 'clear, that when the trench, 46, 

 becomes supplied with water, and the trenches, 34 

 and 45, are empty, that the panes 1 and 15, are 

 in a perfect state of drainage; and this may be 

 sufficient to explain the system, and to shew how 

 every trench operates, either for delivering or drain- 

 ing off the water, at the pleasure of the irrigator. 

 And it should be noted, that this diagonal system 

 enables him to use the smallest quantity of water, 

 as well as the largest, for he can use it only through 

 one system of panes, if necessary, or he can, with 

 great plenty, flow all at the satne moment till the 

 meadow has enough, and then stop the whole out, 

 and leave the trenches to operate only as drains, 

 while the water is working in another meadow. 

 It is not uncommon, for want of such a plan of 

 operation, to see trenches of delivery accompanied 

 by drains, which operate only as drains, and which 

 carry away the water without any power of using 

 it even a second time ; and in other cases we see 

 the water brought on to slopes without any thought 

 of taking it away again, consequently somq parts are 

 much watered, some less, and some, perhaps, not 

 at all. 



Mth, 



