The _depth_ to which the water table should be withdrawn depends, not at all on the character of the soil, but on the requirements of the crops which are to be grown upon it, and these requirements are the same in all soils,—consequently the depth should be the same in all. What, then, shall that depth be? The usual practice of the most experienced drainers seems to have fixed four feet as about the proper depth, and the arguments against anything less than this, as well as some reasons for supposing that to be sufficient, are so clearly stated by Mr. Gisborne that it has been deemed best to quote his own words on the subject: "Take a flower-pot a foot deep, filled with dry soil. Place it in a saucer containing three inches of water. The first effect will be, that the water will rise through the hole in the bottom of the pot till the water which fills the interstices between the soil is on a level with the water in the saucer. This effect is by gravity. The upper surface of this water is our water-table. From it water will ascend by attraction through the whole body of soil till moisture is apparent at the surface. Put in your soil at 60°, a reasonable summer heat for nine inches in depth, your water at 47°, the seven inches’ temperature of Mr. Parke’s undrained bog; the attracted water will ascend at 47°, and will diligently occupy itself in attempting to reduce the 60° soil to its own temperature. Moreover, no sooner will the soil hold water of attraction, than evaporation will begin to carry it off, and will produce the cold consequent thereon. This evaporated water will be replaced by water of attraction at 47°, and this double cooling process will go on till all the water in the water-table is exhausted. Supply water to the saucer as fast as it disappears, and then the process will be perpetual. The system of saucer-watering is reprobated by every intelligent gardener; it is found by experience to chill vegetation; besides which, scarcely any cultivated plant can dip its roots into stagnant water with impunity. Exactly the process which we have described in the flower-pot is constantly in operation on an undrained retentive soil; the water-table may not be within nine inches of the surface, but in very many instances it is within a foot or eighteen inches, at which level the cold surplus oozes into some ditch or other superficial outlet. At eighteen inches, attraction will, on the average of soils, act with considerable power. Here, then, you have two obnoxious principles at work, both producing cold, and the one administering to the other. The obvious remedy is, to destroy their _united_ action; to break through their line of communication. Remove your water of attraction to such a depth that evaporation cannot act upon it, or but feebly. What is that depth? In ascertaining this point we are not altogether without data. No doubt depth diminishes the power of evaporation rapidly. Still, as water taken from a