This tunnel is 700 feet long, and passes under the reservoir (which, nevertheless, is supplied by a pipe from it, ascending on the outside of the rock.)

at the depth of 120 feet,

Glasgow, more populous than Edinburgh, is supplied by steam power from the waters of the Clyde. The peculiarity of the principal works of this city, for there are two the Glasgow works of which we are first to speak, and the Cranston Hill Works

is, that the channels and reservoirs into which the water, percolating through a sandy soil,

passes from the river, are on the left, or south bank of the Clyde, while the most of the

machinery, and the city itself, are on the other bank of course the; water for the engine well must be conducted across the river. The difficulty of such a transmission, at first sight so great, was obviated by the genius of Watt, to whom application was made.

62 PRELIMINARY ESSAY. " This celebrated main of iron pipes, so connected as engineer devised a flexible to adapt its form to the That part laid across the bed of the river, bottom of the river. consisted of pipes, nine feet in length, exclusive of the joints, and having a diameter of 15 inches. Some of the joints were formed in the usual manner, others were made similar to those commonly called ball and socket, or universal joints.* By means of these, the whole train of pipes being properly and firmly connected, the main was laid upon massive wooden frames, consisting of logs laid parallel, and joined together by very strong iron hinges. The pipes and frame were put together on the south side of the river, and the end of the pipe intended for the north side, was stopped with a plug, when a trench having been previously prepared to receive them, by the assistance of machinery, the flexible conduit, with its bed of wood, was hauled across the river, the moveable joints of the pipes, and the hinges of the frames allowing the whole range to assume the form required by the bottom of the Clyde.