388

NICHOLLS'S SEAMANSHIP AND NAUTICAL KNOWLEDGE

transfer of cargo, as the time spent in port is an unprofitable period.
The port speed has to be averaged with the sea speed of the ship when
reckoning up the time taken to complete a voyage. The more round
voyages a ship makes in a year on a given route the more profitable
will the venture be, hence the desire for quick dispatch.

Fig. 1.—A "Jumbo" Derrick lifting
"Stand from Under."

140 tons.

The illustrations, -pages 50 and 55 indicate the usual arrangement
of derricks and winches. The average foreign-going cargo ship has
at least two derricks and winches at ea^ch hatch capable of lifting 5
tons, and a't No. 2 and No. 4 hatches an additional derrick tested to
lift 20 tons, having its heel stepped on deck, the locality being strength-
ened by thickening the deck plating and the adjacent parts so as to