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HISTORY OF

the whole of this canal, that the depth never varies more than from fourfeet to four feet six inches.

The bridge for the aqueduct over the river Irwell, is built all of stoneof great strength and thickness. Every stone in the faces has five squarebeds and sides, well jointed and cramped with iron cramps. There arethree arches over the river Irwell, which, with their piers, are all ofhewn stone of the largest dimensions, and cramped in the same manneras the others. The centre arch is sixty-three feet wide, and thirty-eight feet high above the water, and will admit the largest barges,which navigate the Irwell, to go through with mast and fails standing.—At Stretford, three miles from hence, was the caisson, forty yardslong by thirty-two broad.

At Combroke, three,miles further, is a circular wear to raise the waterof the canal to its proper height: the surplus flows over the nave of acircle in the middle of the'wear; built of stone, into a well, and by a sub.terraneous tunnel is conveyed to its usual channel: there is also a ma-chine to wash the flack, which is worked by water.

In order to feed that end of the navigation which is near Manchester,Mr. Brindley raised, and as it were swallowed up, the river Medlock, bya large beautiful wear, composed of six segments of a circle, built of squarestone, bedded in terras, and every stone cramped with iron: the wholecircumference is three hundred and sixty-six yards, with a circular naveof stone in the middle. The water, when more than sufficient to supplythe navigation, flows over the nave, and down the well as at Combroke;but in order to keep the bed dry during the time the workmen werebuilding this wear, he turned off the greater part of the water by a cutthrough the rock, and invented an engine, which he called a spoon, andwhich he worked, at the end of a lever, by a horse. When this spoondips into the water, a kind of flap door, made of leather, is pressed open,and admits the water till full; and, on being weighed up, the pressure of

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