HISTORY OF ENGINEERING.

Rook I.

443

anil at right angles to the other sills : these rows of sills are to be of the same materials anddimensions as the former, and to be firmly spiked down to the lower rows of sills with

Fig. 450. SECTION THROUGH TIER OP LONDON BRIDGE.

18-inch jagged spikes, as before described. The spaces between the upper rows of sills areto be well fitted and built up level with Bramley Fall, l’ainshaw, or other stone equally good,

Fig. 451.

set in and grouted with mortar similar to that al>ove described, and when made level with thetop of the sills, the whole of the foundations are to be covered with 6-inch beech, elm, or firplanks, to be bedded in mortar, as before described, and to be w’ell-fitted, close-jointed, andfirmly spiked down to the sills with the best wrought-iron jagged spikes, 12 inches long,and ^ inch square, and upon this platform the masonry hereinafter to be described is to bebuilt. Along the front of the abutments, and on each return, and round the entire found-ation of the piers, sheeting piling is to be driven to the depth of not less than 12 feet belowthe top of the above described platforms of the abutments, and 14 feet below the top of theplatforms of the piers, that is, the square parts of the piles are to be of this depth, besides