Mr. Gisborne, in his capital essay on "Agricultural Drainage," which appeared in the _Quarterly Review_, No. CLXXI, says: "We really thought that no one was so ignorant as not to be aware that clay lands always shrink and crack with drought, and the stiffer the clay the greater the shrinking, as brickmakers well know. In the great drought, 36 years ago, we saw in a very retentive soil in the Vale of Belvoir, cracks which it was not very pleasant to ride among. This very summer, on land which, with reference to this very subject, the owner stated to be impervious, we put a walking stick three feet into a sun-crack, without finding a bottom, and the whole surface was what Mr. Parkes, not inappropriately, calls a network of cracks. When heavy rain comes upon a soil in this state, of course the cracks fill, the clay imbibes the water, expands, and the cracks are abolished. But if there are four or five feet parallel drains in the land, the water passes at once into them and is carried off. In fact, when heavy rain falls upon clay lands in this cracked state, it passes off too quickly, without adequate filtration. Into the fissures of the undrained soil the roots only penetrate to be perished by the cold and wet of the succeeding winter; but in the drained soil the roots follow the threads of vegetable mold which have been washed into the cracks, and get an abiding tenure. Earth worms follow either the roots or the mold. Permanent schisms are established in the clay, and its whole character is changed. An old farmer in a midland county began with 20-inch drains across the hill, and, without ever reading a word, or, we believe, conversing with any one on the subject, poked his way, step by step, to four or five feet drains, in the line of steepest descent. Showing us his drains this spring, he said: ’They do better year by year; the water gets a habit of coming to them ’—a very correct statement of fact, though not a very philosophical explanation."