4:20

NICHOLLS'S SEAMANSHIP AND NAUTICAL KNOWLEDGE

thoroughly familiar with the system, the position and operation of all
valves and cocks, the connections which they make and the various
combinations of tank control that are possible. Valves which control
pipes in direct communication with tanks are operated by rods from deck.

Special Precautions must be taken to prevent outbreak of fire, and
oil-carrying ships are well provided with fire-extinguishing apparatus,
nevertheless it is the duty of responsible officers to be continually on
guard and to frequently warn inexperienced and careless persons
against the danger which may arise from smoking, accumulation of
gas in closed spaces and tank bottoms, the creation of sparks when
working with metal tools, or any factional contact that may generate
sufficient heat to ignite inflammable gas.

It is well to distinguish between the Flash point and the Ignition
point of oil. The flash point is that temperature to which oil must
be heated to give off vapour in sufficient quantity when mixed with
air to be ignited by a flame. The ignition point is the temperature to
which the oil must be raised before its surface layers will go on fire.

The flash point is an explosive temperature which is lower than the
ignitioD temperature, the difference varying from 35° to 60° Fahrenheit
in the case of fuel oils. Explosion, therefore, precedes fire. Guard
against explosion. The flash point of spirit is below 75° Fahr.

CARGO PLANS.

I** POfcT

When a mixed cargo is to be loaded for several ports it is desirable
to draw up in advance a rough plan of where the cargo is to be stowed,
so that goods for successive ports may be readily got at in their order
of discharge. An equality of distribution of the goods must also be
considered so that several hatches may be worked in each port and the
discharge at all hatches completed at the same time if possible. The
plan in Figure 11 shows a system of identification marking for a cargo