Improved System of Irrigation. 165 



prettily mapped out by the curves going doivn around the hills 

 and up around the valleys. You can at once perceive where the 



Fig. 3. 



la 2 3 4 5 



water is principally wanted, viz., just above where the curves 

 form the greatest downward bend. In the case before us it is 

 at A, fig. 3. The next thing to be done is, to draw the lines 

 which, upon an average of the whole, will be at right angles to 

 the level ; but in each particular line will deviate from the right 

 angle, more or less, according as the ground is more or less 

 irregular. The plan I adopt is, to put some one to plough after 

 me, and then I walk on before, and, by dragging my feet, leave a 

 sufficient stain to mark where the plough must follow. Care 

 must be taken to go as nearly through the centre of the downward 

 loops as possible. In order to do this, first cut the lines 1, 2, 3, 

 4, 5, and then fill up the intervals by cutting «, Z>, c. They 

 should be from 10 to 15, or more, paces apart, according to the 

 taste of the operator. I do not at all like them to be farther 

 apart than 15 paces, but some persons think that by placing 

 them closer together you cut too much land. 



The next business is to bring in the water, after just lifting 

 the turf out of the gutters already cut. I use, first, a spirit level, 

 and set a mark every 2 poles, allowing the gutter to drop 1 J inch 

 or 2 inches if the nature of the ground will allow of it ; but not 

 less than J inch will do at all well. A much larger gutter 

 is required at J-inch drop than at 2 inches, and, besides, it 

 will not run itself dry so well when the water is turned off. 

 The 2-inch drop gutters will run the water off directly ; the J-inch 

 will scarcely do it at all. Regard must be had to the supply of 

 water required at the farther end. In the case supposed in fig. 3, 

 it is wanted on the rising ground, at the farther end A ; therefore 



