Throughout the length of the ship, then, she is subjected not merely to irregular strains by the peaks and valleys of the waves, but by the distribution of weights. Her structure has to undergo the severest possible stresses, and these are different when the ship is loaded and when she is “light.” If you divide a ship into sections transversely, as is actually done by the designer, you will find that some parts are less buoyant than others, no matter whether your ship is made of wood, iron, or steel. Those sections, for instance, which contain a steamer’s machinery will have much inferior buoyancy, and, indeed, were you to sever them from the ship and seal them up so as to be perfectly water-tight, they would in many cases sink. Therefore, this irregularity of buoyancy has to be met by making the more-buoyant sections help to support the less-buoyant. In actual shipbuilding practice it is customary to regard the greatest stress to a ship as occurring when she is poised on the crest of a wave, and it is usual to suppose, in order to safeguard her manner of construction, that she is poised upon the crest of a wave whose length from trough to trough is equal to the length of the ship, and the height of the wave from trough to crest to be one-twentieth of its length when 300 feet long and below, and one twenty-fifth when exceeding that length.
We have digressed a little from our immediate subject in order to put into the mind of the general reader some conception of the difficulties which Brunel had to encounter when he set to work to produce such a vessel as the Great Western. That she was built on sound lines is proved by the service which she rendered to her owners before she was finally broken up in 1847. On her first return voyage from New York she took fifteen days, and the Sirius seventeen. The Great Western had no such trouble with her “coal-endurance” on her maiden voyage as the Sirius had suffered, for she had reached New York with one quarter of her coals still unconsumed, and the obvious conclusion which came to any reasoning mind was that it certainly paid to build a vessel big enough to carry plenty of fuel. But the Great Western “paid” in more senses than this; and at the end of her first year, her directors were able to announce a dividend of 9 per cent. Thirty-five guineas was the fare in those days, and the largest number of passengers carried on any one of her journeys was 152.
THE “GREAT WESTERN” (1838).
By permission of Messrs. Henry Castle & Sons.
PADDLE-WHEEL OF THE “GREAT WESTERN.”
From the Model in the Victoria and Albert Museum.
Like her contemporaries, the Great Western was fitted with side-lever engines, built by Maudslay. Steam was generated from four boilers, and conducted into two cylinders, her daily consumption of coal being about 33 tons. A model of one of her paddle-wheels, which were 28 feet 9 inches in diameter, [is here illustrated]. This type is known as the “cycloidal” wheel, in which each float, instead of being made of one solid piece of material, is composed of several horizontal widths arranged after the manner of steps in a cycloidal curve, as will be seen by looking at the right-hand of the wheel. It will be noticed that through the space left between each “step” the water could penetrate when the wheel was in the sea, but when revolving out of it, the resistance to the air was diminished because the latter was allowed to get through. As the paddle came in contact with the sea, the concussion was lessened, and thus there was not so much strain on the engines. The Great Western employed the type introduced by Joshua Field in 1833, but this form was brought in again by Elijah Galloway two years later.
So far we have seen steamers running from London and from Bristol to New York. Now we shall see the first steam-vessel crossing from Liverpool to New York. [Facing page 96] is the other Royal William, which was built in 1838 for the Irish passenger trade between Liverpool and Kingstown, and owned by the City of Dublin Steam Packet Company, by whose courtesy this picture is now reproduced. The Royal William was 3 feet shorter than the Sirius, but 2 feet wider, and with a hold just 6 inches shallower. In July of that same memorable year, the Royal William made her maiden trip from Liverpool to New York, having been built and engined at the former port. In was no doubt a great temptation to emulate what the Sirius had been the first to perform, especially as the two ships were so similar in many respects. Outward bound, the Royal William did the trip in about the same time as the Sirius, though her return journey occupied about a day and a half less than that of the other vessel. But these vessels were not big enough, nor seaworthy enough, for the toil of the Atlantic, and both were soon taken off from this route. [The illustration reproduced] is from an engraving after a sketch made of the Royal William, as seen in the Atlantic on July 14th, 1838, when in latitude 47.30 N., longitude 30.0 W., on her first voyage to New York, and the landsman in looking at the waves which the artist has depicted may find some assistance in reading our previous remarks on “hogging” and “sagging” in this connection.