114 TILE DEAINAGE. 



as the wheat was cut. Therefore the drains had all this water to 

 handle. Suppose, now (by P. Q.'s rule), we have one four-inch 

 drain as an outlet for forty acres of laterals. Take Engineer's 

 rate of flow, viz.. four miles per hour, though it will require a 

 pretty heavy grade and full pressure to give as high a rate. If I 

 figure correctly it would take the main nearly ten days to free the 

 field simply of surface-water; and unless there was surface drain- 

 age the shocks would have to stand in the water a week, as 

 thousands of acres did on undrained land in the Black Swamp 

 region near Toledo. 



On my own farm one field (where there was wheat) happened 

 to have 3 four-inch mains to take the water gathered by 12 acres 

 of laterals. The " lay of the field v required three separate mains, 

 and I was determined, from previous experience, to have them 

 large enough, and so used four-inch tile for the lower half of 

 each. They are none too large. Not less than five times within 

 a year they have been crowded to their utmost capacity, even 

 with surface drainage for a short time. In the case of the big 

 rain mentioned, they freed the ground of surface-water in one 

 day that is, as fast as it fell, as they should according to the 

 above estimate. Each had four instead of forty acres to drain, 

 and did it in one day instead of ten. The average grade of the 

 field is three feet to the hundred. 



The rule given by the essayist at Hartford (mentioned by 

 Engineer) is based on correct principles for a limited range of 

 sizes of tiles and variations of grade. It is, in brief, u To find how 

 many acres a given-sized main will drain, square its diameter." 

 Thus, a three-inch main should drain nine acres; a four-inch 

 0113 sixteen, and so on. But for our soil and variable rainfall I 

 am sure this gives far too many acres. I should say, for sixes 

 from three to six inches, and grades less than three feet to the 

 hundred, square the diameter and divide by four. Thus : 



A three-inch main will drain 2J4 acres. 

 A four-inch main will drain 4 acres. 

 A five-inch main will drain 6# acres. 

 A six-inch main will drain 9 acres. 



For heavier grades it may do to divide by three. Thus : 

 A three-inch main will drain 3 acres. 

 A four-inch main will drain o 1 ^ acres. 

 A five-inch main will drain 8^ acres. 

 A six-inch main will drain 12 acres. 



But it must be borne in mind, that, the steeper the grade, the 

 greater the danger of surface wash, which often causes great loss 

 of manure, and even of soil itself. 



My conclusions in brief would be; 1. Have your mains large 

 enough better too large than too small. Don't economize here. 

 It will be "saving at the spigot and wasting at the bung.-' 



2. By " large enough " I mean so large as to take the water as 

 fast as' the soil can filter it and the laterals collect it. 



