1528

THEORY AND PRACTICE OF ENGINEERING.

Book II.

above

Fig. 2810.

plates filling up the spaces over the sheet piling are boltedto the main piles and to each other, and the joints stopped■with iron cement: the plates that receive the mooringrings are cast concave; the whole of the work is backedby a wall of concrete, and the coping is granite. Thesheet-piles are inch thick, and the weight of each pile17 cwt. The length of the wharf is 720 feet, and thequantity of iron used was upwards of900 tons: the height of the sheetis 22 feet, and that of the p'

14 feet: the average rise of the tide isabout 18 feet.

Dykes of Timber filled in with Stonewere formerly much adopted, and atmany of our ports, as well as on thecontinent, we find them ex-ecuted in oak: in someinstances their form is cur-vilinear, to suit the bulgeof the vessel that is to besecured to the quay; andby spreading out the baseto obtain this, additionalstrength is acquired: thewhole is braced horizontallyby a succession of St. Andrew’scrosses, and being afterwards filledin with stone and planked on bothsides, is rendered tolerably secure.

At the Quay of Rouen the sideswere made to incline gradually,and a filling in with courses of ma-sonry contributed to its strength :but this mixture of timber withmasonry is not durable; it fre-quently requires repair, and is onlyadopted where timber is abundantor of little cost.

In another variety of dyke thethickness is obtained by slant-ing one side only, or givingit a greater inclination than theother: the base is in width halfas much more as the height, andstrongly braced and tied together by horizontaltimbers, laid throughout from one side to the other,and further strengthened by inclined struts, abuttingagainst perpendicular timbers which pass entirelythrough its height.

The quays at Rouen are admirable pieces of con-struction, notwithstanding the objection just referredto : in some instances the walls reston sleepers, filled in between withbeton or rubble and mortar, guardedon the waterside by rows of sheet-piling secured to timbers laid in thewall; and where the ground was ina soft state, and could not be de-pended upon, piles ofconsiderable length weredriven and braced, asshown in the figure; theyexcited for years the ad-miration of engineers,and are allowed to bepeculiarly well adaptedfor their situation. figi 28i2j

DYKE IN CARPENTRY.

Fig. 2811.

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QUAY AT ROUEN.

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