WATERTIGHT BULKHEAD DOOES

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kept closed at sea and opened and closed frequently to keep them in
working order.

But large passenger vessels are divided into numerous compartments
by transverse and longitudinal bulkheads, and it is necessary to provide
means for passengers and crew to move freely through the intervening
bulkheads. Large openings have therefore to be made below the water-

Electrical Indicator. A Light for each Door.

Fig. 20.—Watertight Doors. Control Apparatus in Wheelhouse.
line in some of the bulkheads, and in order that these may be closed and
•made watertight at a moment's notice the Stone System of hydraulic
control for bunker and other sliding bulkhead doors is fitted.
The control apparatus is fitted on the bridge. Figure 20 shows
*he bridge control and indicator. The officer on a sucjden emergency
call turns the valve control handwheel, and immediately a pre-warning