A Manual for Naval Cadets

jaws on a chock on the deck, filling up the hollowed out part, and supporting it from the mizen mast head.

Chain reeving lines for screw pendants do not last so well as rope; if they should unreeve by accident, the fish hooks seized in the ends of the pendants will catch the frame and bring the

screw up.

DISTILLING APPARATUS.

The great space occupied by the Engine, Boilers, and CoalBunkers in Steam ships, interfering so much with the stowage of the usual quantity of fresh water, it has been found necessary to provide for a sufficient supply, by means of Distillation, a process that may require explanation.

Whatever substance may be held in solution in water, whether earthy, vegetable, or saline, it does not enter into the vapour or steam which is generated by boiling; and as Steam or Vapour may be reconverted into water by exposure to cold, we have only to collect it in a condensing apparatus, from which the water may be drawn off in a pure state. It is true, that the water which has been mentioned as returning to the boiler from the engine condenser is so freed from salt as to be perfectly fresh, but having gone through so many greasy passages, it is unfit for drinking purposes. A separate chamber is therefore connected with the boilers into which the waste steam, or steam raised for the purpose is admitted, condensed, or distilled, and finally drawn off in the form of purest water.

Fig. 234. represents the condenser with one side removed, showing the internal arrangement, by which the distilling apparatus will be seen to consist of a rectangular tank with two pipes leading into one side of it, one at the lower part, marked "entry," being for the purpose of admitting cold water, and the other at the upper end, and marked "exit," for the purpose of allowing the water admitted through the lower pipe to escape. By means of these pipes, in a manner which will be hereafter shown, a continual current of cold water is kept passing through the condenser; and issuing from the top will be seen a small pipe, marked "vapour exit,” the use of which will be hereafter explained; these form the detail of the outer compartment shown in our diagram. Still referring to fig. 234, the inner com. partment is seen to consist of two small chambers, one placed

above the other at some distance apart, and connected by a series of metal pipes or tubes; and rising from the upper chamber, passing through the outer compartment before mentioned, is a pipe marked "steam," which connects to the steam boilers of the ship; also, issuing from the lower chamber is a small pipe which passes through the outer compartment at the lower end, and from which fresh water is shown to be running.

Having now gone over the outline of our diagram, we proceed to show the action of the various parts before named, during the process of distilling fresh water from the sea. The steam from the boilers enters the steam pipe leading to the upper chamber of the inner compartment (fig. 234.), where it expands as shown by the arrows in our figure, filling the tubes before mentioned, and is there rapidly condensed (returned to water) by the contact of the cold sea water, which has flowed in through the entry pipe, filling the outer compartment, and surrounding the external surfaces of the tubes and inner chambers. The water thus distilled falls into the lower chamber, and runs from thence through the small pipe, marked "fresh water," into the tanks.

Fig. 235. represents the external appearance of condenser when closed and ready for placing in a ship.

Fig. 236. By applying our former remarks to this figure we shall see how the distilling apparatus is placed in a ship. The figure represents the fore hold of H.M.S." Royal George,"

EXIT

PIPE

Fore Hold of " Royal George" fitted with Condensers.

where two of these condensers are fitted, one being on each side of the ship. By looking at this figure, we see that the before named entry and exit pipes pass through holes in the ship's side, and thus open a communication between the condensers and the sea; therefore, the condensers being placed below the water-line, the cold water has a free passage into the outer compartment, where, from being in contact with the tubes of the inner vessel containing the steam, it becomes heated, and hot water being lighter, bulk for bulk, than cold, it rises to the surface of the sea, passing through the upper pipe marked "exit," and thus a continual current of cold water is passing through the outer compartment of the condensers, carrying off the heat which causes the steam in the inner chamber to return to water. We have now to explain the use of the small pipe, marked "vapour escape." The heated water emits a vapour which, if an escape passage were not provided, would accumulate, and in a short time rise to a sufficient pressure to resist the entrance of the cold sea water through the lower pipe. The vapour escape pipe is therefore fitted to the top of the outer part of the condenser, and carried above the water line inside the ship, so as to allow this vapour to escape into the atmosphere. It will also be observed in the diagram (fig. 236.) that there are cocks in each of the exit and entry pipes, for the purpose of shutting off the communication with the sea when the condensers are not at work.

Condensers of this description are made of the various sizes adapted to different classes of ships; those fitted to the "Royal George" are capable of distilling 40 tons of water in 24 hours, and this is obtained at the rate of the expenditure of 1 ton of coals for 7 tons of water.

443

APPENDIX.

A FEW remarks on the personal outfit, expenses, &c., of a Naval Cadet may be of service to candidates.

The following price list of articles necessary for a cadet's first equipment may be taken as a fair sample of such estimates. Some of the prices are less than those charged by outfitters generally; and, as the compiler of this one seems to have given general satisfaction, we may assume that the articles are good, and the prices sufficiently remunerative.

1 Registered Improved Iron-bound Sea Chest, No. 3637., with Improved Zinc Wash Tray & Foot Bath

1 Not Registered, from

1 Dress Coat, Vest and Trowsers 1 Superfine Uniform Round Suit

1 Second Cloth ditto

1 Double-breasted Blue Waistcoat

1 White Cashmere ditto

6 Indian Jean ditto, at 7s. 6d.

1 Watch Coat and Trowsers

£ s. d.

4 10 0

2 10 0