Steamships and their story

by E. Keble Chatterton

The line became the Inman and International Company, and set forth to build a couple of large, powerful steamships which would be in advance of the City of Rome in speed, though not quite so large. Already there had been small twin-screw ships, but the City of New York and the City of Paris were to be driven by twin-screws of a size and power which had not yet been produced. It was fitting that the Inman Line which had introduced the successful screw liner to the Atlantic should also be the pioneers of the very big steamships fitted with twin-screws. These two vessels were taken over in 1893, when the Inman Line became reorganised, and passed from the British flag to sail under the eagle of the American Line. Nowadays they sail from Southampton under the names of the New York and the Philadelphia respectively. [The illustration facing page 166] shows the City of Paris (afterwards called the Paris, and only later still the Philadelphia) getting under way from New York. Her graceful bow, with its bowsprit and figure-head, is reminiscent of the old clipper sailing ships. The high dome of the first cabin dining-saloon will be seen rising in the space between the fore-mast and the bridge, and the promenade deck runs practically the whole length of the ship from the bows to the stern.

The hulls of these steamships are built of mild steel, and in addition to possessing a double bottom throughout their entire length in which a considerable amount of water ballast can be carried, they are divided into fifteen water-tight compartments. The bulkheads of the latter come right up to a height of 18 feet above the water-line, so that in case of collision the ship could still keep afloat even if three compartments were open to the sea.

Their two engine rooms are separated from each other by means of a longitudinal bulkhead, and they are driven by two separate sets of triple-expansion engines. We have already seen that triple-expansion is just the principle of the compound engine carried one stage farther, and if the desire for attaining the high speed contemplated were to be gratified it was inevitable that this method should have been adopted. With the exception of a very few quadruple-expansion engined ships, such as the Cunard Ivernia, the White Star Baltic, and the German Kaiser Wilhelm II., most modern liners which have not been fitted with turbines are of the triple-expansion type. It may not be out of place, therefore, very briefly to explain the working of this.

THE “CITY OF PARIS” (NOW THE “PHILADELPHIA”) (1893).

From a Photograph. By permission of the American Line.

THE “OPHIR” (1891).

From a Photograph. By permission of Messrs. Anderson, Anderson & Co.

The steam, then, enters the cylinder above the piston-rod by means of a valve, but when it has half-filled the cylinder and the stroke is also half completed, the supply of steam is cut off. But the piston-rod does not for that reason come to a standstill: owing to the expansive force of the steam the rest of the stroke is completed when the steam has occupied twice the space it did at the time it was cut off—that is, when the half-stroke had been made. Having, therefore, now completed its work in this cylinder, instead of being allowed to escape, the steam is conducted to a much larger cylinder than the first, for the steam still retains much of its expansive force. In this second cylinder, the same thing occurs again, but when it is admitted to a third, it has already lost much of its pressure. It does its work, and having come through the third cylinder has thus undergone “triple expansion.” Now that it has completed the stroke it passes into the surface condenser already referred to, where it is suddenly chilled and converted into water again, and the vacuum thus formed tends to pull the piston back. In the olden days, as we have seen, the vacuum was made by means of the jet condenser, but now it is done by what is known as the “surface” condenser. It is by means of the latter that the fresh water is able to be used again and again. Otherwise, a steamship could only carry enough fresh water for a few days’ voyage, salt water being not used for the boilers, but merely for circulating through the pipes of the condenser to keep them cool. As the steam comes out from the lower pressure it impinges on the sea-water cooled tubes and so falls to the bottom of the condenser as water. It is then pumped into a tank by means of the air-pump, and from the tank it is pumped back again to the boilers by a feed pump, passing on its way through a filter in order that any oil which may have been gathered in the cylinder may be extracted. It now passes through feed-heaters, where it is heated by exhaust steam from the auxiliary machinery, and so when the condensed water again enters the boiler it is almost at boiling point.