Sometimes, especially in the case of overhead travelling cranes for very heavy loads, the chain is a special pitch chain, formed of flat links pinned together, and the barrel is reduced to a wheel provided with teeth, or " sprockets," which engage in the links.
Ducks, cranes and other aquatic birds abound in the delta.
For dock-side jib cranes the use of electric power is making rapid strides.
The use of cranes is of great antiquity, but it is only since the great industrial development of the 19th century, and the introduction of other motive powers than hand labour, that the crane has acquired the important and indispensable position it now occupies.
Hand cranes are extremely useful where the load is not excessive, and the quantities to be dealt with are not motive powers.