890 NICHOLAS'S SEAMANSHIP AND NAUTICAL KNOWLEDGE
for discharging. Hatches, however, should not be touched when the
cargo is a valuable one until they have been surveyed, and this is usually
done if heavy weather has been experienced? and there is a possibility
of damage to the cargo.
The Union Purchase or "married gear" is a favourite arrangement
for loading and discharging. It consists of two derricks, both fixed,
one guyed to plumb the hatch, the other to plumb overside. The
falls from both derricks are shackled to the same cargo hook. The
sling of goods m the hold is hooked on and hove up with the midship
fall until it is clear of the hatch coaming The slack of the fall from the
other dernck is then run in quickly and the midship fall eased off until
the load is wholly borne by the overside derrick and lowered into a
lighter orvon to a quay. The cargo hook is then hove back again to
take the next sling.
This method, for speedy work, requires two quick acting, reliable
winches and operators. It is suitable for light loads of about 5 to 10
cwt. per sling, but the extra strain imposed on the falls and guys as a
result of the cross pull is a disadvantage.
Swinging Derrick.—When there are no obstructions in its way a
swinging derrick having a long reach is, perhaps, the speediest and most
reliable arrangement for working heavy slings of bag cargo up to a
ton and a half in weight, especially if it be fitted with an adjustable
span so that it may be regulated to plumb the hatch and also overside.
It can pick up and land the goods anywhere within the radius of its
swing, thus accelerating the work of handling the goods and making up
the sets for slinging.
The outboard guy, when discharging cargo, is usually led to a
steam winch and the light derrick is sometimes pulled inboard by
leading the guy through a block aloft and securing a heavy weight,
a "dead man," on the end of it. There may be a prejudice against the
"dead man'* method of controlling the inward swing owing to the danger
of someone getting hurt by the descending weight.
The Double Lift method is sometimes used for the rapid handling
of mixed general cargo, viz., one derrick lifting off the quay and landing
on deck, and another derrick picking off the deck and lowering into
the hold, using skidboards where required.
More men are required per stevedore gang for the double handling,
but rope whips substituted for wire falls and worked on the winch ends
make for increased speed which may offset the increased labour cost.