On Draining. 189 



part of the drain, and proceed downward, so that the mud 

 raised in the operation may not run in among the stones, 

 and fill up any part of the. interstices. 



It is much recommended to all farmers, in low and moist 

 situations, frequently to perambulate their farms, for the 

 purpose of examining the state of their drains, and discover- 

 ing every obstruction ; nor ought even the trace of the mole, 

 crossing an open drain, to escape their notice ( ia7 ). 



2. Covered Drains. As open drains rather diminish the 

 extent of surface, and are sometimes injurious to stock, 

 covered drains are in many cases preferred. Here we shall 

 consider, The season for executing them ; The mode of 

 doing it ; Their size; Whether hollow or filled; Ma- 

 terials for filling ; Distance from each other ; Duration ; 

 The expense ; The state of the ground ; and, The 

 impediments and enemies they have to encounter. 



1. The summer is, in general, the best season for execut- 

 ing such drains, because the labourers can then work with 

 more comfort -, the materials for filling can be more easily 

 collected ; the land is in the best state for bearing the car- 

 riage of stones; and more work can be done in a day ( ia8 ). 



2. Drains intended to be ultimately covered, are some- 

 times begun to be made by the plough, as being the least 

 expensive mode. But only small drains can be made in 

 this way ; and as drains, in general cases, ought to be at least 

 four feet deep, spades of different dimensions must be em- 

 ployed. The additional expense is amply repaid, as the 

 work is done more effectually ( I39 ). The trench, however, 

 is often begun by the plough, and finished by the spade ( 13 ). 



3. The size of covered drains, must be regulated by the 

 quantity of water to be conveyed away. In point of width, 

 there should only be room to work, unless, from the soft- 

 ness of the soil, a greater slope is necessary. An overwidth 

 increases the quantity of materials requisite to be used in 

 filling, which, in many situations, is an object of no small 

 consideration. The depth should be such, as to allow a 

 proper quantity of earth above the drain, that the materials 

 in it, and what covers them, may not be injured by the 

 pressure of the horses or cattle in the act of ploughing. 



4. Covered drains are frequently hollow, where the run 

 of water is large, or the materials good. This last is the 

 case, when the drain is made of stones, either inserted in a 

 triangular shape, or regularly built and covered by flags ; or 

 where common or draining bricks or pantiles are made use 

 of. These are preferable to stone in two respects : they can 



