The main drains are at a considerably higher level than the surrounding lands, the water in them only prevented from drowning the low-lying fields again by their great and solid banks, fourteen to sixteen feet high, and about ten feet in breadth at the top. These banks, indeed, form in many districts the principal roads. Perilous roads at night, even for those who know them well, and one thinks with a shudder of the dangers encountered of old by local medical men, called out in the darkness to attend some urgent case. Their custom was--perhaps it is in some places still observed--to mount their steady nags and to jog along with a lighted stable-lantern swinging from each stirrup, to throw a warning gleam on broken bank or frequent sunken fence. At an interval of two miles along these banks is generally to be found a steam pumping-engine, busily and constantly occupied in raising water from the lodes and dykes in the lower levels and pouring it into the main channel. The same process is repeated in the case of raising the water from the field-drains into the smaller dykes by a windmill or "skeleton-pump," as it is often called. It is a work that is never done, but goes forward, year by year, and is paid for by assessments on the value of the lands affected by these operations. Commissioners, themselves local landowners and tenants, and elected by the same classes, look after the conduct and the efficiency of the work, and see that the main drains are scoured by the "scourers"; the banks duly repaired by the "bankers" and the "gaulters"; the moles, that might bring disaster by burrowing through them, caught by the "molers"; and the sluices kept in working order. The rate imposed for paying the cost of these works is often a heavy one, but the land is wonderfully rich and productive. Nor need the Fenland farmer go to extraordinary expense for artificial manure, or for marling his fields when at length he has cropped all the goodness out of the surface soil. The very best of restoratives lies from some five to twelve feet under his own land, in the black greasy clay formed from the decaying vegetable matter of the old forests that underlie the Fens. A series of pits is sunk on the land, the clay obtained from them is spread over it, and the fields again yield a bounteous harvest.