1839.] 



THE CIVIL ENGINEER AND ARCHITECT'S JOURNAL. 



433 



Figure 3, Transverse Section of Coffer Dam and part of ihc Lock. 



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M I I n I I I I ' 



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20 



30 



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Referevee to Engravings, similar letters refer to similar parts of Coffer Dam. — P, piles. W, wales. T, iron ties. — B, braces. C, clay puddle R, the river. 

 H, Trinity high «'ater-mark. L, ditto, low water-mark 18 feet below. .S, surface of river hank, dredged 12 feet below low water-mark. bl. cl., substratum 

 of blue clay. The inner row of piles to coffer dam are cut oil' level with t.pl, the timber platlorm and form sh^'et piling to the latter. J, jetty projected 70 

 feet into the river for loailing the bargs with the excavation of the locks and dock. 



Lode. — pi, platform of masonry, gr, groove lor caisoon. M. masimry. S, pointed sill of gates. Q, quoin to inner post of lock gates. P. R, rows of 

 piles 12 feet long and Si inches in diameter, upon the top are spiked heads or cross sills 12 by 12 inches, upon which is laid 6 inch planking. Between the 

 he ds and cross sills is filled in with rubble. S.p, sheet piling at the toe of the wing walls. i,ar, and B, invert to lock chamber oi brickwork, b.st, bond 

 stones 15 inches thick. C, stone coping 18 inches thick. 



c, I, centre line of lock and coffer dam. 



FORM OF SHOES. 

 Figure 4, for Giiage Piles, Figures 5 and 6, for Bay Piles. 



TIE BOLT FOR COFFER DAM. 



Fig. 7, Plan of Head. 



Fig. 8, Bolt. 



Fig. 9, Plan of Nut. 



Scale one inch to the foot. 



_.7.._.-.5. 



Scale one inch to the foot, 

 the same as to the main dam, leaving sufficient space between the 

 piles to fill up the bays the same as above, the temporary waliiigs 

 are then to be removed, and one of 12 inches square to be put on, as 

 shewn by the drawing, and bolted, as above, so as to secure the piles to 

 the main dam, the bolts not to exceed the distance of 5 feet apart, 

 and every second bolt to pass through the two rows of main dam piles 

 and waiings, this dam is then to be tilled in with clay as above ; the 

 inner row of piles, at the dist;ince of .5 feet from the main dam to 

 have a double waling 12 by G inches bolted within one foot of the top, 

 and to be firmly braced from the inside, and the top part of the dam 

 must be tied to the shore with chains to prevent it going outwards at 

 low vi-ater. 



Along the western side of the present lock or gut which passes 

 along the eastern side of the entrance lock, there is to be a coffer dam 

 14U feet in length, with returns at each extremity, to consist of the 

 same materials as the middle row of the main coffer dam to the en- 

 trance lock as directed by the engineer. The timber, iron, clay, bricks, 

 and all other materials for the dams to be found by the contractor, who 

 is also to find all pile-engines, steam-engines, stages, &c., and to the 

 satisfaction of the engineer. A circular trunk 3 feet diameter with 

 sluices, for letting the tide flow in ;ind out, are to be placed through the 

 dam. The mud, gravel, and other matter, now upon the space where 

 the coffre dam is to be constructed, is to be removed by the contractor 

 to the level of 12 feet below low water-mark of a spring tide, and in 

 an uniform inclination to the lowest part of the bed of the river, oppo- 

 site the said cotfre dam. 



( To he coiilinued.) 



2 2 



