DRAINAGE. 119 



levels were taken at all of the points of intersection, showing the 

 elevation of those points above an imaginary plain underlying the 

 whole farm. This was all shown upon the map, and upon the same 

 map contour lines, — or lines of equal elevation, — at differences 

 of level of one foot, were laid on in a different color from the 

 hnes marking the squares. In the accompanying map the black 

 lines show the lines defining the squares, and the figures at their 

 intersections show the elevation of the land at that point above 

 the imaginary-level plain. The red lines show the lines of 

 equal elevation along the surface of the land ; of course the line 

 of steepest descent of the land is in all cases at right-angles to 

 these. The blue lines show the location of the drains. 



Before a stroke of work was done upon the land, the levels 

 were taken at the intersections of the black lines, and these and 

 the contour lines were drawn upon the map ; and in every in- 

 stance, in advance of the staking out of the drains upon the 

 ground their location was drawn upon the map and was staked on 

 the ground directly from the map. This insured the locating of 

 each drain in what, not guessing, but actual measurement, showed 

 to be the right place ; and enabled an estimate to be made in 

 advance of the quantity and sizes of tiles required, and of the 

 amount and cost of the work to be done. 



By reference to the map it will be seen that the following rules 

 have been adhered to, so far as circumstances would admit : — 



First. — Always to run the lateral drains parallel to each other, 

 and down the deepest descent of the land; in some cases they 

 are not parallel, and in others they run in a direction slightly 

 different from the steepest inclination — the object being always to 

 harmonize those two conflicting requirements so as to produce 

 the best average result. 



Second. — To lay no drain on such a course that water running 

 through it would flow more rapidly in the upper than in the lower 

 part of the drain ; it has been necessary in this matter also 

 to deviate somewhat from the rule. This has never been 

 done, however, except where the reduced rate of fall was suffi- 

 cient to insure so rapid a flow as to carry off any silty matters 



