America was slow in changing from wood to iron, because the cost of iron was so high. We had wood in abundance, numerous yards for the construction of wooden vessels, and were the builders of the best type of wooden ships. In 1853, the year just referred to for Great Britain, twenty-two per cent of the tonnage of the vessels built in this country was in steamships, but only an inappreciable portion was in iron vessels. The adherence of American ship-builders and owners to wood is well illustrated by the action taken by the owners of the famous but unfortunate American Collins line, established in 1847. The company began, in 1850, to run four palatial steamers, built without regard to cost, and supplied with luxurious appointments, some of which are retained in vessels of the present day; but the company built the ships of wood and propelled them with paddle-wheels. The great American ship-building firm, William Cramp & Sons, founded in 1850, did not begin constructing iron ships till 1870. Even in 1898, the tonnage of wooden vessels constructed was one and a half times the steel and iron tonnage. About twenty-six per cent of our merchant marine, foreign and domestic, is now made up of iron and steel vessels.
The next important step in maritime progress, following the adoption of iron and the screw, was taken about 1870, when the compound engine came into general use. Though the compound engine had been used on a small vessel in France as early as 1829, it was first extensively adopted as the result of the rapid development in steam navigation which took place in the seventies. In the compound engine the steam, instead of being used in only one cylinder in passing from the boiler to the condenser, exerts its force in two or three cylinders, and even in four, in the quadruple expansion engines. This results in a great economy in the amount of fuel used. In the earlier marine engines the pressure of steam in the boilers was thirteen pounds to the square inch, and the consumption of coal per horse-power per hour was five and one half pounds; whereas, at the present time, a pressure of two hundred pounds per square inch is maintained, and the fuel used has been reduced to less than one and a half pounds per hour for each indicated horse-power.
Ten years after the compound engine came into general use, the cheapened cost of steel made it possible to adopt steel in the place of iron in the construction of hulls. This may be regarded as marking a fifth epoch-making step in the progress of commerce; because the steel ship was stronger, lighter, and able to carry more cargo than iron vessels of the same size. The substitution of steel for iron in the British yards was made rapidly. In 1879, only ten and a quarter per cent of the tonnage constructed on the Clyde was of steel; but in 1889 the per cent had risen to ninety-seven.
During the past twenty years there have been many improvements made in the construction and appointments of ships; but the more important changes have consisted in dividing vessels, by means of bulkheads, into several water-tight compartments, and in substituting twin screws for the single screw. The Inmans placed twin screws on the City of New York in 1888, and since then their use has become general on the larger ocean liners. The twin screws add somewhat, though not greatly, to the speed of vessels; but they render ships much safer and less liable to be disabled. An ocean steamer with twin screws and water-tight compartments can suffer any one of the common accidents—such as breaking of one of its shafts, losing one of its screws, having its rudder damaged, or one of its engines give out, or having its side punctured by collision—without being disabled. Although ocean travel still has its dangers, the risks at the present time are far less than they were a half or a quarter of a century ago.
The technical progress of commerce during the nineteenth century is well summarized by Mr. Henry Fry in his book on the History of North Atlantic Steam Navigation, written in 1895. He says:—
“The Comet of 1812 has multiplied into twelve thousand steamships, measuring over sixteen million tons.... Her twenty tons have been multiplied into a ship of eighteen thousand; her forty feet to six hundred and ninety-two feet; and her four horse-power to thirty thousand in a single ship. Symington’s four-inch cylinder has grown to one hundred and twenty inches; the pressure of steam in the boiler has increased from thirteen pounds to two hundred pounds on the square inch; the two hundred and forty-three knots, the maximum of the Great Western in 1838, to five hundred and sixty; and the average speed from 8.2 to 22.01 knots, while the consumption of coal has decreased from about five and one half to one and one half pounds per indicated horse-power per hour.”
The century’s naval technical progress is epitomized in the White Star liner, the Oceanic. The length of this mammoth vessel is over an eighth of a mile, being 705 feet, 6 inches. 13½ feet longer than the Great Eastern was. When loaded, the Oceanic draws 32 feet, 6 inches of water, and on that draft her displacement is 28,500 tons. The figures for the Great Eastern were 25 feet, 6 inches, and 27,000 tons. The capacity of her engines is 28,000 horse-power, or two and one third times the capacity of those in the Great Eastern. The pressure in her boilers is 192 pounds to the square inch, or ten or twelve times that in the boilers of her famous predecessor. Though not built for speed, the Oceanic can average 500 miles a day, or sixty per cent more than the Great Eastern did. The Oceanic will accommodate 400 first-class passengers, 300 second-class, 1000 third-class, and a ship’s company of 394, making a total of 2104 persons. In this regard, however, her figures are fortunately less than those of the Great Eastern, for that vessel was designed to carry 4000 persons, besides crew. These figures regarding passenger accommodations indicate in a forceful way the great advancement that has been made in the comforts of ocean travel during the past forty years.