smaller thread of less pitch is used. Otherwise the construction of the doors is substantially the same (Fig. 60).

16

A cast-steel frame, shaped as shown in Figs. 59 and 60, is bolted to the bulkhead. The sides are formed, with a taper of in. to a foot, to correspond with the frame on the door. The door is formed of a steel plate, with a steel casting to stiffen it, shaped as shown. The section of the door shows very clearly the construction, and how the door jams in between the bulkhead casting and the check plate. The top edge of the casting is provided with a metal nut, with a thread to correspond with that on the spindle. This spindle extends from the top of the opening to the main deck, the thread, of course, extending only sufficient to open the door. The door can be closed by a set of gearing from below, as well as from above, and, when necessary for purposes of escape, it can be worked from either side of the bulkhead.

The doors between engine and boiler-rooms, and to coalbunkers, have their sills kept well above the inner bottom.

Horizontal Sliding Doors.-Doors of this type (Fig. 62) are fitted to important bulkheads below water (and to a few above

water), to which vertical doors cannot be fitted because of the lack of sufficient head room. The opening in the bulkhead is bounded by a steel casting, shaped as Fig. 61. This casting is secured to the bulkheads by bolts. At the bottom and top there is a groove, having a taper of in. to a foot, in which the door slides, and in which the door jams when closed. The door is formed by a steel plate, well stiffened by a steel casting, shaped as shown. The weight of the door is taken by two wheels. The inside edge of the door has a gunmetal strip all round, which engages with the bulkhead casting. The leading edge of the door jams into a number of clips on the edge of the frame, and the following edge of the door has some back pieces, which jam against the back of the bulkhead frame. The door has two horizontal steel racks, and into these two gunmetal pinions engage, these being rotated by a vertical spindle. This spindle extends to the main deck, so that the door can be worked from above if desired.

FIG. 61.

CLIP ON FRAME

The door can also be closed at the door by a spanner, working on a nut on the spindle.

A disadvantage with horizontal doors is the existence of the bottom groove. The dirt from the traffic soon fills

up the groove,

TO TAKE RUB OF SILL PLATE

PINION

METAL STRIP

Door

C.B. WEIGHT.

FOR LIFTING

FOR
SPANNER

SILL PLATE.

TAPER TO THE FOOT

VERTICAL SECTION

FIG. 62.--Horizontal sliding watertight door.

and this gets hard and prevents the door from closing. To obviate this a sill plate is fitted over the sill. When the spindle for closing is first turned, it turns the sill plate up out of the way, to allow the door to slide along and shut. When the door is again opened, the sill plate automatically drops over the groove again.

The vertical spindles for closing watertight doors are always so arranged that a right-hand motion closes the door. The deck.

plate at the main deck, where the spanner is worked, is provided with an indicator to show whether the door is shut or not. The spanner, however, should always be turned as far as possible to close the door, as frequently after the gearing is worn the indicator may point to "shut" when the door itself is not completely shut.

Screens are fitted to the doors of coal bunkers on the inside to protect the doors from the pressure of the coal, and thus enable the doors to be opened and closed when the bunkers are full (see Fig. 120).

A book is supplied to the commanding officer of each ship giving a list of the watertight compartments, with their capacity in cubic feet, the boundaries and means of closing, and the places at which the doors can be closed. In addition to this the means of pumping and ventilating each compartment is given. A specimen page of such a book is given at the end of Chapter IX.

In the Admiralty circular above mentioned attention is drawn to the defects found in watertight doors, and the methods to be adopted to keep them efficient.

Sluice Valves are fitted to the lower parts of certain bulkheads to drain water from one compartment to another. These valves are worked like a small vertical door, with a spindle extending to the main deck, having an indicator on the deck plate. In recent ships no sluice valve is fitted on the collision bulkhead.

Automatic Ventilation Valves. In the more recent ships the artificial ventilation is arranged so that the main transverse bulkheads are not pierced. In previous ships, however, the ventilation was provided by a series of fore-and-aft trunks, having louvres at intervals (see Fig. 105). These trunks were supplied with air from large steam-driven fans. In this way the watertightness of the bulkheads was completely destroyed, and the openings had to be provided with automatic valves, arranged to shut automatically if water rose in the compartment on either side. Provision was also made for shutting all these valves if desired by pipes led from the main or upper deck.

Two of these valves are shown in Figs. 63 and 64. Both operate by a float, which rises if water enters, and this float then releases a balance weight, which closes the opening. In the case of Beck's valve (Fig. 63) an ordinary slide valve is used. In Broadfoot's valve (Fig. 64) the valve turns round and closes the

opening. In either case the small opening in the bulkhead for conveying water to the float from the opposite side is automatically closed when the balance weight falls.

These valves under the conditions on board ship, are found to

be far from efficient, and require jamming home by hand. All the bearing surfaces should be kept clean (see Admiralty circulars mentioned below).

Inspection of Watertight Doors.-As so many doors have to be left open for access throughout the ship, even supposing an action is proceeding, it is obviously of the highest importance that they should all be in perfect working order, and the crew well exercised in closing them, so that they can be readily closed in any time of emergency. The following extracts from the "Steam Manual" gives the instructions regarding this:

"The watertight doors and sluice valves are placed under the charge of the Chief Engineer. All the Engineer Officers must make themselves acquainted with the positions and methods of closing of watertight doors. All watertight doors are to be kept clear for immediate closing. No fitting of any kind is to be allowed which will require to be removed before the door is closed. Watertight doors and sluice valves are to be opened and shut regularly once a week to ensure their being in good working order. The Chief Engineer, besides preparing the station bill, is to take such measures as he may deem necessary to ensure that every person under his control shall know his post and be capable of performing his duty, so that in case of emergency the watertight doors and sluices may be closed without confusion."

Similar instructions are given in the King's Regulations.

Recent instructions have been issued in Admiralty circular, S. 32111/1903, of January 29, 1904, in regard to watertight doors and hatches. See also S. 31157/1903, of January 9, 1904, for Admiralty circular referring to H.M.S. Prince George.

Automatic Doors.-The following extract from Sir William White's report on the loss of the Victoria may be quoted with reference to the suggestion frequently made that automatic or "self-closing" doors should be adopted instead of existing arrangements:

"This suggestion is a revival of one made long ago, then carefully considered and put aside after certain experimental doors had been tried.

"Automatic arrangements are applied in valves to ventilating trunks and other small openings in bulkheads and platforms. Even in such cases the feeling of the Naval Service has led to the automatic fittings being supplemented by the means of closing the valves when desired. In doors and scuttles the risks of the automatic appliances failing to act, or of solid materials being carried into openings by a rush of water, and preventing doors from closing properly, would be much greater. These considerations have led to the retention of existing fittings, the design of which provides that, when properly closed and secured, doors and hatchway covers shall be as strong as the neighbouring partitions, and watertight under considerable pressure.

"There is no difficulty in making automatic appliances. It is a question of what plan secures the maximum of safety under the working conditions of the Royal Navy. With large numbers of disciplined men, familiar with the fittings, and constantly drilled in their use, it is possible to close and properly secure all the doors, etc., in a battle-ship in three to four minutes, or possibly a less time for ships after long periods in commission.

"In the Victoria, no orders were given to close doors until one minute before collision. It is established by the evidence that the doors, etc., were in good order. The failure to close doors, therefore, was due entirely to the insufficiency of time available, especially in compartments breached by the collision.

"Under these circumstances no new argument in favour of the use of automatic doors seems to arise out of the loss of the Victoria."

* Parliamentary Paper, No. C. 7208/1893.