At intervals along the line of his intended conduit he first sinks shafts, which he then connects with one another by galleries, seven or eight feet in height, giving his galleries a slight incline, so that the water may run down them freely, and continuing them till he reaches a point where he wishes to bring the water out upon the surface of the plain.

Here and there, at the foot of his shafts, he digs wells, from which the fluid can readily be raised by means of a bucket and a windlass; and he thus brings under cultivation a considerable belt of land along the whole line of the _kanat_, as well as a large tract at its termination.

These conduits, on which the cultivation of the plateau depends, were established at so remote a date that they were popularly ascribed to the mythic Semiramis, the supposed wife of Ninus.

It is thought that in ancient times they were longer and more numerous than at present, when they occur only occasionally, and seldom extend more than a few miles from the base of the hills.
By help of the irrigation thus contrived, the great plateau of Iran will produce good crops of grain, rice, wheat, barley, Indian corn, doura, millet, and sesame.

It will also bear cotton, tobacco, saffron, rhubarb, madder, poppies which give a good opium, senna, and assafoetida.
Its garden vegetables are excellent, and include potatoes, cabbages, lentils, kidney-beans, peas, turnips, carrots, spinach, beetroot, and cucumbers.