Note 102 — Chapter VII · RAILWAY BRIDGES AND VIADUCTS.
Reading edition
See note at the end of this chapter for experiments on ropes and chains. The crabs were designed and made specially for this duty. Each had two barrels, grooved to receive the chain, which was passed several times round both barrels, so as to get sufficient grip; and it was in this way possible to wind in with the crabs any length of chain without having to stop to fleet, as would have been the case had a single-barrelled crab been used.
These crabs were subsequently used at the floating of the Saltash trusses, and at the launch of the ‘Great Eastern.’
A similar arrangement was applied in the paying-out machinery of the Atlantic cable, and is still used for the picking-up gear in the ‘Great Eastern.’