THE DRAINAGE OF FARMS. 89 



of the main drain should be 3J or 4 feet below the surface ; and 

 says that a drain ten inches wide, and twelve inches deep, will 

 discharge the water from a hundred acres. Many persons, in 

 undertaking the draining of flat lands, are discouraged by the 

 difficulty of finding an outfall for the water j but he deems that 

 one foot fall in a hundred yards, with a drain of the above dimen 

 sions, may be relied on. &quot; It has been proved, in practice, that a 

 watercourse 30 feet wide and 6 feet deep, giving a transverse 

 sectional area of 180 square feet, will discharge 300 cubic yards 

 of water in a minute, and will flow at the rate of one mile per 

 hour, with a fall of no more than 6 inches per mile.&quot; It is his 

 advice that this main drain should be covered as well as the side 

 drains ; but others recommend that it should be left open, that 

 it may be always easy to watch the running of the side drains 

 which empty into it. Three objections, which, among others, 

 lie against leaving the main drain open, such as the falling in 

 of the sides, the loss of ground, and the danger of the access of 

 vermin to the side drains, (where they are formed with tiles,) 

 are obviated by Mr. Morton, in an ingenious manner, as I saw 

 on Lord Ducie s model farm. I have already slightly referred 

 to it. The main drain, in this case, runs through the lowest 

 part of the land ; but it is made so broad and flat that the grass 

 can be mowed down to the very watercourse, or a cart could be 

 driven, without overturning, on the very edge or sides of it, 

 though this would never be advisable, for fear of injury to the 

 drains. The farm road, in this case, is made at about the dis 

 tance of sixteen feet from the centre of this open drain, or brook. 

 In this case, then, there is no loss of land, and no bridges are 

 required in the crossing. Where the side drains enter the main 

 drains, one link in the chain of pipes is omitted, and the remain 

 der of the distance is laid with small broken stone, which allows 

 of the passage of the water, but forbids the access of any vermin 

 into the drain. 



The main drain having been formed, Mr. Smith advises, next, 

 the cutting of a drain at the top of the field, and across the whole 

 breadth of it, from which all the side drains are to commence, 

 and thence run exactly parallel with each other into the main 

 drain. The depth of this transverse drain must not be more 

 than that of the drains which may be said to take their rise from 

 it, and lead into the main drain. Besides the great main drain, 

 8* 



