1530

THEORY AND PRACTICE OF ENGINEERING.

Book II.

they require to he loaded withstone, or filled in solid; andwhere this is done, plankingand sheet-piling are requiredto keep the materials so de-posited within the frameworkfrom washing away.

The foundations of walls con-structed in the sea or in deeprivers require the greatest at-tention on the part of the en-gineer : where the soil is soft*and cannot be depended upon,it is necessary not only to pileit closely all over, but to layon the heads of thepiles a piece of wholetimber, and then fillup level with rubble;another series of tim-. bers of the samescantling should belaid in a transversedirection, and whenbrought level byanother filling-in ofrubble masonry,the wall is builtupon it: such wasthe system adoptedby Perronet whenconstructing thebridge at Neuilly .

At Rochelle similarprecautions wereadopted for the wallsof the docks, whichwere faced with free-stone and backedin with brick: a rowof sheet-piling wasdriven along the

Fig. 2818.

NEUILLY FOUNDATIONS.

D

□

Fig. 2819.

NEUILLY FOUNDATIONS

1 j ; '[=.. > :

f¥\

Fig. 2820.

ROCHELLE.

whole length of the footing, to prevent the water from acting upon any portion of the foundation.

Another system of holding in the upright fenders is by irons worked into the solid wall,or they may be made to pass round a row of horizontal timbers, halved into the upright atthe levels of high and low water.

Fig. 2821.

Fig. 2822.

Stone facings backed with brick, when made to batter, afford the best protection to thesides of a dock or pier that can be devised : upright fenders of oak or fir secured by iron