HISTORY OF

3 si 4

having happened since it was finished; nor has the water oozed through,to the detriment of the canal, but all the purposes expected have beenwell answered.

An Aqueduct is a structure to convey a canal over rivers, morasses,or low grounds. I have already described those over the river Irwell,and across the Sale-moor, constructed by the late Mr. Brindley for theduke of Bridge water: but the largest in Great Britain (if not in Europe)is that lately finished by Mr. Whit worth, the engineer to the Forth andClyde navigation in Scotland, over the river Kelvin, which consists offour arches, and carries the canal over a valley sixty-five feet deep, andfour hundred and twenty feet in length ; exhibiting a grand essort of in-genuity and labour. In the course of this canal, for a considerable way,there is an embankment twenty feet high: the-water is sixteen feetdeep. Two miles of the canal is cut through a deep morass. At Kir-kintilloch the canal is carried over Loggie water on an aqueduct archninety feet broad. This arch was thrown over in three stretches, having.only one centre thirty feet wide, which was shifted on small rollers fromone stretch to another; a mode ingenious and novel for an arch of thissize. The joinings are fair, and as equal as any other part of the struc-ture ; which is admitted to be a piece of very sine masonry.

To supply this canal with water was a very arduous task. There faone reservoir of fifty acres, twenty-four feet deep; and another of seventyacres, twenty-two feet deep, in which many rivers and springs termi-nate. These, it is expected, will afford a sufficient supply of water at alltimes.

Plate II. shews a design for an aqueduct which crosses a river the width-of the three centre arches; and, to occupy the remaining space usefully,the extreme arches are converted into warehouses.

a. The