Chap. XIV.

OX PILES AND PILE-DRIVING.

1079

drv, but when under water a machine is requisite : this is composed of a horizontalframe formed by the three piecesA. A, A, 4 inches square, framed intotwo cross pieces B, B, and a verticalframe formed by the two uprightsC, C, each about 4J inches square.

At the foot of these is placed thesaw l, which is kept tightened byscrewing the iron at the other ex-tremity of the upright timbers, so asto bind or secure the blade. Inorder to give motion to the saw, aworkman is placed to each of thehandles at E, and alternately pushesthem backwards and forwards in thedirection A A, whilst another on thescaffold directs their labour, and hold-ing a rope R, so places the saw thatit at once puts a kerf into the headpile when required. This machineis usually mounted on wheels, andenabled to traverse the scaffold freely.

At the bridge of Choisy such amachine was worked by a carpenter and six labourers, and who in 2 5 minutes sawed off a pile10 to 12 inches diameter, placed at 3 feet 8 inches below the cross-pieces A, A, and thus cutoff about 22 in a day of ten hours, the rest of the time being employed in altering theposition of the machine and the scaffold. The saws cut with the most perfect correctness,when the frames which guide them slide in such a manner that the cross pieces A, A areallowed to remain in the same horizontal plane ; but the upright pieces C, C cannot wellbe made more than 9 or 10 feet in length below' the cross-pieces A, A; therefore, when itis necessary to cut piles at a greater depth, some other means must be resorted to.

Labelye , in building Westminster bridge, appears to have been the first who appliedsuch a machine, in 1738, to cutting off piles. This engineer published a brief report in1751 upon the various systems he adopted for the construction of this bridge, and it is tobe regretted that he did not complete the account which he announced as preparing: manyof Labelye’s ingenious inventions have been copied without acknowledgment, and someeven patented since his time; this is evident by a reference to the account preserved bythe late Air. Thomas Gayfere, who was senior apprentice to Mr. Jeff, the master masonemployed at Westminster bridge.

For cutting off piles at more than 1 0 feel, or up to 15 feet below the water, the in-vention by Messrs. Voglie and Cesart at the bridge of Saumur may be considered ingenious,and was very successful: it was a modification of the one already described, and withfour men to work the saw, and a fifth to adjust the saw against the pile, they wereenabled to cut off a pile in five or six minutes, and could in the course of 12 hours cutoff 22 piles, allowing for the moving and adjusting the machine.

De Cessart's Machine for cutting off the Heads of Piles under Water _The machine was

supported by a scaffolding, composed of three pieces of timber, 32 feet in length; eachcarried at its extremity a roller, 18 inches long and 8 inches in diameter, which were runon timber made perfectly smooth and level, placed equidistant along the length of the pier,and supported on the tops of piles.

The object of this machine was first to cut off the piles at a uniform height, and that theupper part of the pile should he cut truly level, that four men should work the saw withease; that the pressure of the saw against the head of the pile should be regulated by oneman, as the timber produced more or less resistance; that the operation should be performedwith as much facility when the head of the pile was absolutely out of sight, as when it ap-peared above the water; that it should be practicable to cut another slice, if the firstdid not effectually level the pile; that the machine should embrace the head by grapplingand taking a firm hold; that when necessary to clean or reset the saw blade, it should bedone with facility, and that the small rolling scaffold should advance by degrees alongthe breadth of the pier, while the large scaffold carried it along to another row of piles.

For the first operation, the saw blade is drawn back by a regulator; the machine israised 6 inches by the four perpendicular rods, which work with racks and pinions at thetop, and is then advanced towards the pile; when it is lowered to the level of the intendedcutting, an iron sounding rod serves as a gauge to mark this, and having established thelevel for the machine to work, the grapples are tightened by means of ropes, and the sawingis commenced : this is performed by four men, moving alternately the iron rods, whichwork in grooves at the top. and by means of other jointed rods give an oscillating motion,- 3 z 4

CI TTINO OFF PILES.