manner in which he finished the bed of this canal, and made it impervious to water, may be cited as a notable illustration of the engineer's practical skill, taking into account the early period at which this work was executed.

Not the least difficult part of the undertaking was the formation of the canal across Trafford Moss, where the weight of the embankment pressed down and “blew up” the soft oozy stuff on each side; but the difficulty was again overcome by the engineer's specific of clay-puddle, which proved completely successful. Indeed, the execution of these embankments by Brindley was regarded at the time as something quite as extraordinary in their way as the erection of the Barton aqueduct itself.

The rest of the canal between Longford and Manchester, being mostly on sidelong ground, was cut down on the upper side and embanked up on the other by means of the excavated earth. This was comparatively easy work; but a matter of greater difficulty was to accommodate the streams which flowed across the course of the canal. This was, however, provided for in a highly ingenious manner. For instance, a stream called Cornbrook was found too high to pass under the canal at its natural level. Accordingly, Brindley contrived a weir, over which the stream fell into a large basin, from whence it flowed into a smaller one open at the bottom. From this point a culvert, constructed under the bed of the canal, carried the waters across to a well situated on its further side, where the waters rising up to their natural level, again flowed away in their proper channel. A similar expedient was adopted at the Manchester terminus of the canal, at the point at which it joined the waters of the Medlock.

It was a principle of Brindley's never to permit the waters of any river or brook to intermix with those of the canal except for the purpose of supply; as it was clear that in a time of flood such intermingling would be a source of great danger to the navigation. In order, there

fore, to provide for the free passage of the Medlock without causing a rush into the canal, a weir was contrived 366 yards in circumference, over which its waters flowed into a lower level, and from thence into a well several yards in depth, down which the whole river fell. It was received at the bottom in a subterranean passage, by which it passed into the river Irwell, near at hand. The weir was very ingeniously contrived, though it was afterwards found necessary to make considerable alterations and improvements in it, as experience suggested, in order effectually to accommodate the flood-waters of the Medlock. Arthur Young, when visiting the canal, shortly after it was opened up to Manchester, says, "The whole plan of these works shows a capacity and extent of mind which foresees difficulties, and invents remedies in anticipation of possible evils. The connection and dependence of the parts upon each other are happily imagined; and all are exerted in concert, to command by every means the wishedfor success." ""*

Brindley's labours, however, were not confined to the construction of the canal, but his attention seems to have been equally directed to the contrivance of the whole of the arrangements and machinery by which it was worked. The open navigation between Worsley Mill and Manchester was 10 miles in length. A large basin was excavated at the former place, of sufficient capacity to contain a great many boats, and to serve as a head for the navigation.

It is at Worsley Basin that the canal enters the bottom of the hill by a subterranean channel which extends for a great distance,-connecting the different workings of the mine, so that the coals can be readily transported in boats to their place of sale. A representation of the basin is given in the annexed cut. It lies at the base of

* Six Months' Tour through the North of England,' vol. iii., p. 258. Ed. 1770.

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a cliff of sandstone, some hundred feet in height, overhung by luxuriant foliage, beyond which is seen the graceful spire of Worsley church. In contrast to this scenic beauty above, lies the almost stagnant pool beneath. The barges* laden with coal emerge from the mine through the two low, semi-circular arches opening at the base of the rock, such being the entrances to the underground workings. The smaller aperture is the mouth of a canal of only half a mile in length, serving to prevent the obstruction which would be caused by the entrance and egress of so many barges through a single passage. The other archway is the entrance of a wider channel, extending nearly six miles in the direction of Bolton, from which various other canals diverge in different directions.

In Brindley's time, this subterranean canal, hewn out of the rock, was only about a mile in length, but it now extends to nearly forty miles in all directions underground. Where the tunnel passed through earth or coal, the arching was of brickwork; but where it passed through rock, it was simply hewn out. This tunnel acts not only as a drain and water-feeder for the canal itself, but as a means of carrying the facilities of the navigation through the very heart of the collieries; and it will readily be seen of how great a value it must have proved in the economical working of the navigation, as well as of the mines, so far as the traffic in coals was concerned.

At every point Brindley's originality and skill were at work. He invented the cranes for the purpose of more readily loading the boats with the boxes filled with the Duke's "black diamonds." He also contrived and laid down within the mines a system of underground railways, all leading from the face of the coal, where the miners

* The barges are narrow and long, each conveying about ten tons of coal. They are drawn along the tunnels by means of staples fastened to the sides. When they

are empty, and consequently higher in the water, they are so near the roof that the bargemen, lying on their backs, can propel them with their feet.