In the English tables of the cost of drainage by the Drainage Companies, an estimate of $1.25 per acre is usually put down for "superintendence," which includes the engineering and the supervision of the whole process of opening, laying and filling, securing outfalls, and every other process till the work is completed. The general estimate of the cost of drainage is about $25.00 per acre, and this item of $1.25 is but a small per centage on that amount. The point has been dwelt upon here, more for the purpose of impressing upon land-owners, the importance of employing competent skill in the laying out of their drainage works, than because the expense thus incurred, forms any considerable item of the cost of the whole work. 2. _Excavation and Filling._ The principal expense of drainage is incurred in the excavation of the ditch, whether it be for tiles or for stones. The labor of excavation depends much upon the nature of the soil to be moved. "Draining on a sound clay," says the writer of a prize essay, "free from stones, may be executed at a cheaper rate per rod, in length, than on almost any other kind of soil, as, from the firmness of the clay, the work may be done with narrow spades, and but a small quantity of soil requires to be removed. The draining of wet sands or grounds, or clays in which veins of sand abound, is more expensive than on sound clays, because a broader spade has to be used, and consequently a larger amount of soil removed; and draining stony or rocky soils is still more expensive, because the pick has to be used. This adds considerably to the expense." Great stress is laid, by all experienced persons, upon using narrow spades, and opening ditches as narrow as possible. It is somewhat more convenient for unskillful laborers to work in a wide ditch than in a narrow one, and although the laborers frequently protest that they cannot work so rapidly in narrow ditches, yet it is found that, in contract work, by the rod, they usually open the ditches very narrow. Indeed, it will be found that, generally, the cost of excavation bears a pretty constant proportion to the number of cubic feet of earth thrown out. It will surprise those unaccustomed to these estimates, to observe how rapidly the quantity excavated, increases with the increased width of the ditch. To enable the reader accurately to compute the measurement of drains of any dimensions likely to be adopted, a table and explanations, found in the Report of the Board of Health, already quoted, are given below. The dimensions, or contents of any drain, are found by multiplying together the length, depth, and _mean_ width of the drain.