Chap. XXVI.

SEA AND DOCK WALLS.

1529

^ In facing the sides of apier or dock wall withtimber, series of land-tiesare requisite to prevent thepressure outwards, as wellas to act as struts againstits action inwards: a strongcapping of timber framedto the heads of the piles, abrace secured by iron straps,and a horizontal tie halved°n to the sides and heads°f the piles, may be so puttogether as to endure for

Fig. 2813.

ROCHELLE.

Fig. 2814. QUAY AT ROUEN.

Fig. 2815

a length of time, if secure fromthe ravages of the teredonavalis.

The Piers of the HumberBasin are 18 feet across theirtop; the main piles are 14inches square; those of theouter wall of the same dimen-sions ; those of the inner wall12 inches by 6 inches; the capsill 12 inches by 10 inches; thejoists 7 inches by 4 inches ; theties 12 inches by 6 inches;sheet-pilling 6 inches thick,and the planking 3 inches..

In the construction of piersof this kind great attentionshould be paid, so that theyhave sufficient strength toresist the force which is oftenexerted during storms againstthem. Up to a certain height