516

HISTORY OF ENGINEERING.

Book I.

end of the chain was then made fast to that which hung perpendicularly from the apex ofthe pier, on the Caernarvonshire side. The other end of the chain to be suspended was

Fig. 525.

WAIN TACKLE FOR RAISING THE CHAINS.

fastened to two blocks of great power, the tension of the chain at this time being equal to40 tons.

Fig. 526.

SADDLES FOR CARRYING THE MAIN CHAINS.

SECTION.

After the blocks were made fast to the chain, two capstans and two preventive capstans,each worked by 32 men, commenced raising, and within two hours and twenty minutesfrom the movement of the raft from theshore the last bolt was fixed, which com-pleted the entire length of the first chain,three of the men employed passing alongit. And by the 9th of July the otherfifteen chains were secured, and the entireline of suspension completed.

Vertical rods. — These are placed atequal distances of 5 feet, and are fastenedto the sixteen suspension chains. Theiron sleepers or transverse roadway barsare bolted to the lower ends, and to eachof these 111 sleepers four vertical rods areattached transversely, making altogether444.

Timber roadway .—The first tier of planksw T as laid across the iron sleepers on the24th of September, 1825, there being threealtogether, the lowest 3 inches thick, themiddle and upper each 2 inches ; the last is laid transversely to the width of 8 feet, withside guides to prevent any injury from the carriage wheels. The planks are all spikedtogether, and between each layer was a coating of Borrodaile’s patent felt saturated withboiled tar.

Fig. 527.