Chap. VIII.
5G3
When the cylinder had reached the rock, a frame, which fitted it, was introduced intothe upper end, and sunk by means of two half hundred weights, and in the middle of theframe, through a hole 4 inches square, was passed a funnel which tapered to 3 inches atthe bottom ; this was driven down to the rock, and the sand enclosed in the funnel wascleared out, by a cylindrical iron tube, 3 inches diameter, and 3 feet in length, which hada valve fixed within 2 inches of the bottom, resting on a small ring, fastened to the insideof the tube, on the top of which was a screw, by which it was attached to a set of boring-rods.
It was then passed down to the bottom of the square wooden pipe, and working byshort and quick strokes, the sand and gravel were brought by the agitation of the waterabove the valve ; the tube was then drawn out and emptied; this was continued until thewhole surface of the rock within the square tube was perfectly clean.
Through the square directing pipe a jumper was then passed, worked by a lever on theupper scatfold, until a hole 20 inches in depth, and 2£ in diameter, was bored into the rock,into which an iron dowel, 2 inches square, might be placed ; this was effected by fasteningit to a square socket, made in the end of 1^-inch square iron bar, a small cord beingattached to it, to prevent its falling out of the socket whilst lowering the square directingpipe to the rock: when it had arrived there, it was driven into the hole in the rock bystriking the head of the bar several times with a hammer. After it was driven 18 inchesinto the hole, the timber was lifted up by a sudden jerk, which broke the cord, and left thedowell in its place, the frame and square directing pipe being also lifted out of thecylinder. The pile to be let down had two hoops round its lower end, and a hole cut toreceive the end of the iron dowell already placed upright in the rock.
On the lower end of this pile were nailed four other pieces, so as to increase its size to 22inches, the diameter of the cylinder, by which means it could be securely placed exactlyover the iron dowell by a stroke of the pile-engine.
To the chain fixed at the top of the cylinder a lever was applied, 50 feet in length, thefulcrum of which was laid on the top of the main piles, and the other end lifted by ropesand blocks from the mast of a sloop. It required a purchase of 50 tons to start thecylinder; it was lifted up over the tops of the piles by the aid of ropes and blocks. Thehead of the pile so fixed was then forced against the inner side of the leading frame, and ascrew bolt put through both. The apparatus was then shifted to the others, until thewhole of the main piles were fixed. Temporary leading beams were then fastened to theheads of the first piles, at 15 or 20 feet apart, round the outside of the main leadingframes, and these spaces filled up by driving other piles, side by side, down to the rock.The lower temporary leading frame was then taken off, the inside braces put in, whichrested on brackets fastened to the main piles.
The outer row of piles was placed in front of the cofferdam, by means of a float made ofpieces of fir timber 1 foot square, and 40 or 50 feet in length, fastened together by spikingothers across them. This float, 14 feet in length, filled the space between the rows of piles,and was not only kept steady by them, but served to regulate and maintain their paralleldistance.
When the outer row was driven, a leading beam made by fishing was bolted to theoutside of the piles, on a level with the inside leading frame ; a temporary leading framewas then fixed on the inside of the outer row of piles, 1 foot lower than the outside beam ;a scaffold was erected on the top, and an outside leading beam bolted, at the same levelwith the leading frame on the inside.
The space between the first-mentioned piles was now filled up by others set closetogether, and driven down to the rock. The bank and puddles on each side of the dambeing by this time brought forward as far as the inner row of piles, the connecting boltswere placed through each pile opposite the middle of the leading frame, through which itpassed, across the puddle, and through the front leading beam on the outside of the outerrow of piles. Each of these connecting bolts svas fastened by a strong cotterel througheach end, with a strong iron plate under them; two of these bolts passed through eachof the main piles in front of the dam, one through each of the leading frames and theother 1 foot below low water of ordinary spring tides, at which level the leading beams onthe outer row of piles was fixed. The two rows of piles were maintained in their positionby pieces of timber being joined on each side of the main pile on the inside of the dam, andspiked down on the outside of the leading beams. When the banks and cofferdam werefinished, and the engine commanded the water, the works were proceeded with in the usualway, and after enough of the rock had been removed the masonry was commenced. Thelocks on this canal are of unusually large dimensions; the whole work, forming a junctionbetween the two seas, was opened at the end of the year 1823.
Artificial embankments have already been described, as made for the canal, 400 yards inlength beyond high water-mark on the shore of Loch Beauley at Clachnacharry, where thefoundations were of mud so soft that an iron rod could be thrust down 55 feet with ease.
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