Irrigation of that species called catchwork [Editor's note: catchwork, or catchdrain, is an artificial water-course for throwing water on lands that lie on the slopes of hills] might be carried to a great extent on the sides of the hills and mountains; but the grass produced, though greater in quantity, would no longer be of the same nutritive and aromatic quality that it is at present. In various places, where irrigation has been employed, the finer Poï¾µ, Festucï¾µ, Cynosurus, and Anthoxanthum have given way to cock's-foot grass, and the coarser species of Agrostis, Avena, and Poa. The hilly district, besides being favourable for the growth of trees and grasses, is also particularly so for the establishment of machinery to be driven by water. This district has scarcely at all been employed in this manner; but, were it found necessary to resort to water as a primary power instead of steam, the hills and mountains of Cumberland and Westmoreland would be found of immense value, and the water which might be collected on them, in zones, as hereafter described, would probably be more than sufficient to move all the machinery now in use on the island. To produce a maximum of effect by the water which falls on any hill, it ought to be collected in zones, the upper zone being formed 50 or 100 ft. lower than the summit of the hill or mountain, and each succeeding zone being made at a distance below the other, of a foot or two more than the diameter of the water-wheel to be driven by it. The number of wheels of 50 ft. diameter which might thus be driven between the foot and the summit of a conical mountain 1500 ft. high, and whose base covered an area of two thousand acres, might easily be calculated; and the calculation would furnish data for estimating the power of any number of irregular mountains. It may possibly happen that in some future age, when the coal mines are exhausted, the manufactures of Britain will be transferred from the plains of Lancashire, Warwickshire, Staffordshire, Nottinghamshire, and other counties, to the highlands of Scotland, to North Wales, and to the lake scenery of Cumberland and Westmoreland. To those whose patriotism can embrace a period of a thousand years, this view of British manufactures may be consolatory. As to coal for domestic fuel, if all the coal, not only in Britain, but in the whole world, were exhausted, it would be easy for every family to grow its own fuel; even without any farther improvements in the mode of application, than those which have been already suggested (Vol. VI. p. 145.), or any new discoveries in chemistry. An easy method of expressing, from common air, sufficient heat for all domestic purposes, may probably be discovered long before coal is exhausted.
