"Of the durability of common brick, when used in drains, there is a remarkable instance mentioned by Mr. George Guthrie, factor to the Earl of Stair or Calhoun, Wigtonshire. In the execution of modern draining on that estate, some brick-drains, on being intersected, emitted water very freely. According to documents which refer to these drains, it appears that they had been formed by the celebrated Marshal, Earl Stair, _upwards of a hundred years ago_. They were found between the vegetable mould and the clay upon which it rested, between the 'wet and the dry,' as the country phrase has it, and about thirty-one inches below the surface. They presented two forms--one consisting of two bricks set asunder on edge, and the other two laid lengthways across them, leaving between them an opening of four inches square for water, but having no soles. The bricks had not sunk in the least through the sandy clay bottom upon which they rested, as they were three inches broad. The other form was of two bricks laid side by side, as a sole, with two others built or laid on each other, at both sides, upon the solid ground, and covered with flat stones, the building being packed on each side of the drain with broken bricks." In our chapter upon the "Obstruction of Drains," the various causes which operate against the permanency of drains, are more fully considered. CHAPTER VII. DIRECTION, DISTANCE, AND DEPTH OF DRAINS. DIRECTION OF DRAINS.--Whence comes the Water?--Inclination of Strata.--Drains across the Slope let Water out as well as Receive it.--Defence against Water from Higher Land.--Open Ditches.--Headers.--Silt-basins. DISTANCE OF DRAINS.--Depends on Soil, Depth, Climate, Prices, System.--Conclusions as to Distance. DEPTH OF DRAINS.--Greatly Increases Cost.--Shallow Drains first tried in England.--10,000 Miles of Shallow Drains laid in Scotland by way of Education.--Drains must be below Subsoil plow, and Frost.--Effect of Frost on Tiles and Aqueducts. DIRECTION OF DRAINS.