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and successful effort to establish a steamship service across the Atlantic. They built, in 1840, the “Britannia,” “Acadia,” “Columbia,” and “Caledonia,” – the first ships of the now celebrated Cunard Line.

      The Inman Line was founded in 1850, the Guion Line in 1866, and the White Star Line, which now shares the great Atlantic trade with the Cunard Company, was established in 1870.

      The evolution from sail to steam involved changes in the design of the hull of a ship. At first it was considered that to turn a sailing-ship into a steamer it was simply necessary to fit a hull designed for a sailing-vessel with a steam engine. It was soon, however, discovered that the fine lines and deep keel required to carry sail were not required in a steamship, and in course of time full-bodied hulls with square bilges without keels were adopted.

      An iron steamer is but a rectangular girder or tank with the ends sharpened, the co-efficient of fineness varying from 62 to 78 degrees, according to the speed or deadweight capacity required. In 1860 Sir Edward Harland, with a view to easy propulsion, introduced steamers into the Mediterranean trade with a length of ten times their beam. These were so successful that when he built the fleet for the White Star Line he carried out the same principle, thereby also securing steady sea boats. He also introduced central passenger saloons and cabins, which speedily made the White Star ships very popular. Cabin accommodation placed in the centre of the ship has now become general. Some further modifications in design have taken place; ships have, relatively, now less length and more beam, and the cabin accommodation is built up citadel fashion in the middle of the ship.

      The most notable evolution has, however, been in size and speed. The “Britannia,” built in 1840, was 1,200 tons, with 8½ knots speed. She was followed by the “Great Britain,” in 1843, 3,270 tons; she was, however, too large for the times, and did no good. The “Great Eastern,” built in 1855, was of 18,915 tons, and 12 knots speed, and was also a failure, although if she had been given sufficient power she would probably have hastened the era of large and fast vessels.

      The demand for speed was for some years the governing feature in the design of steamers in the Atlantic trade, and to a smaller extent in the Eastern trades, in which the carrying of coal for long voyages has also to be considered. The increase in power required to obtain high speeds necessitated the adoption of twin screws, and with the still higher powers required by the “Mauretania,” “Olympic,” etc. (60,000 h.p.), four propellers are found necessary.

      In the Atlantic trade, the “Arizona,” built by John Elder & Co. for the Guion Line, was the first of the “Atlantic greyhounds.” She was quickly followed by the “Alaska” and the “Oregon,” the latter being built in 1882, with a speed of 19 knots. She was the fastest ship of her time, and became the property of the Cunard Company. She was again eclipsed by the Cunard ships “Umbria” and “Etruria,” in 1885, with a speed of 19½ knots. In 1888 the “City of Paris” and “City of New York” had attained a speed exceeding 20 knots. For some years no improvement in speed was obtained until the advent of the “Campania” and “Lucania,” in 1893, with a tonnage of 12,900 and a speed of 22 knots.

      Although steamers thus gradually increased in size and power, the “Oceanic,” built in 1899 for the White Star Line, may, I think, claim to be the pioneer of the great Atlantic liners. She was 16,900 tons and 704 feet long, and 21 knots speed. She was quickly followed by the “Lusitania” and “Mauretania,” built for the Cunard in 1907, with a tonnage of 33,000, and a speed of 24½ knots. They were again eclipsed in size by the “Olympic,” “Aquitania,” and the “Imperator,” all about 50,000 tons; but the “Mauretania” still holds the blue riband of the Atlantic for speed. It is scarcely safe to say that the last big ship has been built; size is only limited by commercial considerations and the depth of water available in our harbours, as an iron ship, being a girder, her length is limited by the depth which can be given to the girder. The cost of construction may, however, limit the size of ships, at all events, for some years.

      Chapter III

      THE EVOLUTION OF THE MARINE ENGINE

      The steamship as a practical proposition developed slowly, being retarded by the dilatory evolution of the marine engine. The first serious effort to apply steam power to vessels of any size dates back to only 1838-1840, years which witnessed the establishment of the Royal Mail, the Peninsular and Oriental, and the Cunard Steamship Companies. Their first vessels were steamers of 1,200 tons, having a speed of eight or nine knots. Such vessels were not formidable competitors of the old packet ships, except in the passenger trades; their average passage across the Atlantic, occupying from thirteen to seventeen days, not being a great improvement upon the passages of the sailing-packets. The ships of the Dramatic Line averaged 20½ days, and those of the Black Ball Line 21 days.

      The advantage of the greater regularity in the passages of the steamer was, however, obvious, and greatly stimulated invention. The improvements in the paddle engine were slow. We were a long time getting away from the side-lever engine, working at a low pressure. The “Britannia,” built in 1840, was 1,200 tons; her engines indicated 740 horse-power, giving a speed of 8½ knots. The “Scotia,” the finest paddle steamer ever built, and the last of the great paddle boats, was built in 1860, and had the same type of side-lever engine, but her tonnage was 3,871, with an indicated horse-power of 4,800, giving her a speed of 13 knots. The most rapid passage made by the “Britannia” was 14 days 8 hours; the most rapid made by the “Scotia” was 8 days 15 hours.

      The screw propeller was invented in 1836, but for a long time it was thought to be inferior to the paddle as a means of propulsion, and there was some difficulty in applying the power to the screw shaft. The side lever in various forms was tried, but proved a failure. The “Great Britain,” 3,270 tons, launched in 1843, had engines which worked upward on to a crank shaft, and the power was brought down by endless chains to the screw shaft. This did not prove satisfactory. Then we had oscillating engines working a large geared wheel fitted with wooden teeth to increase the revolutions of the propeller. Then came the direct-acting engines with inverted cylinders, which for years were almost the universal type of engine, and were a very efficient form of low pressure engine.

      The compound engine revolutionised the steamship trade, ensuring such economy of fuel as to permit of long voyages being successfully undertaken. The compound engine developed into the triple expansion engine; the object being to get the last ounce of power out of the steam by first using it in a high pressure cylinder at 180 lbs., then passing it into a larger cylinder, using it expansively, and finally passing it into a still larger cylinder at about 8 lbs. pressure, and again allowing it to expand. The triple expansion engine came into general use in 1886.

      The turbine, invented by Sir Charles Parsons in 1897, has effected a revolution in the engines of large size. The principle is simply to allow steam at a high pressure to impinge upon blades fitted to a rotor which it revolves on the principle of the syren. The steam is afterwards used expansively in a second rotor working directly upon the screw shaft. The advantage of a turbine engine is its simplicity – few working parts and a saving in weight and space; its disadvantage is that a separate turbine has to be employed to obtain sternway. Recently, geared turbines have been introduced which are lighter, slightly more economical in fuel, and are sweeter running machines.

      It is noteworthy that whereas gears were necessary in olden times with engines working at a low pressure to speed up the propeller shaft, with turbines gears are used to reduce the revolutions.

      Meantime, greater boiler efficiency was being obtained. The “Britannia” worked with a pressure of 12 lbs. This was gradually increased to 30 lbs. in boilers constructed in 1868, and this was practically the range of pressure during the period of single-expansion engines. The salt water used in these boilers caused them to become quickly salted up, which not only diminished their efficiency but shortened their lives, and it was not until the compound engine was invented by John Elder that cylindrical boilers, working at a pressure starting at 60 lbs. and increasing to 190 lbs., were introduced. These proved a great success. By the use of fresh feed water and replenishing it from the condensers, salting was prevented and the life of a boiler greatly increased.

      No further great improvement in the boiler has taken place. The water-tube boiler is still in an experimental stage, and

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