splashing over the sides when disturbed during high winds. The large pipe, A, is securely bolted at the bottom of the tank, and forms a shield or funnel through which the supply pipe, B, passes upwards into the tank. C is an overflow, or waste pipe, to carry away any surplus which may find its way into the tank after the water has risen to its fixed maximum height. All the contact surfaces of the cast-iron tank-plates must be accurately chipped or planed, and fitted to ensure water-tight joints. Stayrods must be placed at frequent intervals, connecting the vertical or outer plates to the horizontal or floor plates. When required to hold more than 20,000 gallons, it is better to make the tank in two parts, by placing a permanent plate petition across the middle, in reality making two separate tanks, which can be connected or disconnected at will. The double tank arrangement gives additional strength, and possesses the advantage that the one tank can be emptied and cleaned out while the other remains in service.

Water-tanks constructed of wrought-iron or steel plates are usually made circular in form, with vertical sides. The floorplates must be either carried on small girders, as in the cast-iron tank, or be strengthened internally with angle-irons, tee-irons, and tie-rods. The rivetting must be well done, all joints sound and watertight. This class of tank must be kept well painted, or oxidization will take place very rapidly. The arrangement of inlet, waste-pipe, and delivery pipe may be the same as for the cast-iron tank. Although frequently seen abroad, these circular wrought-iron tanks are not often adopted at home. By many the appearance of the circular tank is considered inferior to one of neat rectangular shape, and the form of the round tower does not lend itself so conveniently for use as a pump-room or store.

There may be no practical difficulty in constructing a large circular wooden vat or water-tank, but there cannot be any great actual economy, except in those countries where suitable timber is very cheap, and iron very dear. The wooden tank must be made of selected materials, and by skilled workmen ; but however carefully constructed it cannot be expected to last so long as an iron tank. In many parts of the United States of America there are excellent examples of the circular wooden tank, strongly put together, and covered with a light ornamental roof. Numbers of these wooden tanks have been erected there in places where the cost of carriage alone of an iron tank would

have been a serious item, and where suitable timber was fortunately close at hand.

In cases where engines are watered direct from a water-tank, a simple delivery-valve, as shown in the sketch (Fig. 458), will answer the purpose. This valve has to be pulled open by the chain and lever, D, and when released falls with its own weight, and is kept close by the pressure of the water above. The delivery-pipe should not be less than 7 or 8 inches in diameter, to accelerate the filling of the tenders. Where water has to be delivered to engines at two or more places in a station-yard, and the supply derived from the same principal tank, the result may be obtained either by laying down 7 or 8-inch main pipes from the principal tank to separate water-columns, or by erecting two or more pedestal water-tanks, similar to Figs. 459 to 462, each of which holds a little more than the average quantity for one tender, and can be fed from the principal tank by a comparatively small pipe of 3 or 4 inches in diameter. It is simply a question of expense-whether it is cheaper to lay down a long length of 7 or 8-inch main pipe and ordinary water-columns, or to adopt the small pipes and pedestal tanks.

Figs. 459 to 462 are sketches of a medium-sized pedestal water-tank to hold 1200 gallons. The supporting column must have a very wide base, bolted down to a solid foundation. The tank itself, made circular in plan, is generally constructed of light plates of wrought-iron or steel, the lower portion or floor of tank being very securely attached to the vertical column. Notwithstanding their top-heavy appearance, these pedestal tanks can be made very firm and steady if enough width be given to the base-plate, and the tank properly fixed to the column. Water is led into these pedestal tanks by a small pipe passing up inside the supporting column, and the delivery may be effected by a simple valve, as explained for Fig. 458.

Fig. 463 shows one type of water column for watering engines. The wide base-plate is bolted down on to a foundation of stonework, brickwork, or concrete, and the main supply pipe (not less than 7 or 8 inches in diameter) is carried up inside the column, and connected with the screw valve, A, which regulates the delivery to the tenders. The curved top, which forms the outlet, and carries a leather hose, works on a swivel joint, and can be swung round, either to the right or left, for convenience of supplying engines on one or two standing-lines. The delivery

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valve can be opened or closed by the small hand-wheel B, which is conveniently accessible to the man on the tender. On the above sketch (Fig. 463) the water column is shown placed at an ordinary normal distance from the rails; but in cases where there is considerable space between the two lines of rails, or where a platform intervenes, the swinging arm may be extended out to the necessary length, and counterbalanced as shown in Fig. 464.

CHAPTER VI.

Comparative Weights of some Types of Modern Locomotives.

Weights of Locomotive Engines.-The demand for higher speeds of passenger trains, with more conveniences, luxuries, and consequent increased weights in the carriages, has naturally led to greatly increased power and weight of the locomotives devoted to the passenger service. Although these engine weights have so largely increased during the past twenty-five years, there is nothing to indicate that they have yet reached the maximum. The tendency is still to increase, and will doubtless continue, so long as the permanent way can be made to sustain such enormous rolling loads. Locomotives for goods trains have also increased in power and size, but perhaps not in the same proportion as those for the passenger service. There is not the same disposition to expedite the transit of goods and minerals, which do not deteriorate during a long journey. Perishable articles, such as fish, fruit, and milk, are usually conveyed by passenger trains, or trains set apart specially for the purpose.

The heavier engine doubtless possesses greater tractive power, but apart from the question of tractive power is the allimportant one of steadiness and safety on the rails. A locomotive passing round a curve, even at a moderate velocity, produces disturbances in proportion to the capability of the machine to adapt itself to the altered position, and if both the engine and permanent way are constructed so as to be almost unyielding, then destructive wear and tear and increased risk of derailment must ensue. The adoption of the four-wheel bogie truck to the locomotives on our home and continental linesalthough very slow in coming-has contributed greatly to their improvement, enabling the weight to be distributed over a longer, yet more flexible wheel-base, affording greater facility and comparative safety in traversing curves; and rolling, or