Stevens had driven a small boat with screws before Fulton built the Clermont, but John Ericsson, a Swede, was the first to develop screw propulsion in a practical manner. His first work was done in England, where he built a screw steamer 45 feet long with which he made a speed (April, 1837) of ten miles an hour on the Thames. Then he towed the American packet ship Toronto at a speed of four and a half miles an hour. On July 7, 1838, an iron vessel 70 feet long by 10 wide, and having a draft of 6 feet 9 inches, named the Robert F. Stockton, was launched at Laird & Co.'s yard, Birkenhead, England, for Captain Robert F. Stockton, U. S. N. It was fitted with an engine and an Ericsson screw. It was then brought to America under sail, and set to work under steam as a tug on the Delaware River, where it earned much money for many years.
In 1839 Ericsson came to the United States and built the screw steamship Princeton for our navy, the first warship of the kind in commission.
In the meantime Francis P. Smith, an English farmer, was developing screw propulsion, and succeeded in convincing the Admiralty that the screw was a practical device, with the result that many experiments were tried and the screw was much improved.
In introducing the screw, two difficulties were encountered. The engines of the day gave only about twenty-five revolutions to the minute, and it was therefore necessary to introduce some sort of multiple gearing between the engine-shaft and the screw shaft; for a screw should turn at seventy-five times a minute, or more. The other defect of screw propulsion was found in the strain of the shaft upon the stern of the ship. No combination of timbers in a wooden ship could resist that strain for any great length of time. To the English, however, this was a matter of no moment, for iron had already been used for building hulls. The first of these iron ships was the Aaron Manby, launched in London, in 1820, but the iron ship that first really influenced the British merchant marine was the Great Britain, built for the Great Western Steamship Company at Bristol, in 1843. She was a big ship for her day (322 feet long), and she was not only a profitable cargo carrier, but, having been stranded on the coast of Ireland, she endured the poundings of the storms of an entire winter, and was then hauled off, repaired at small expense (considering the storms she had endured), and when put at work again was found to be as serviceable as ever.
As the Great Britain was driven by a screw the use of iron screw ships soon became fashionable in the British merchant marine, and the more rapidly because they were much more economical in the use of coal.
Lindsay (History of Merchant Shipping) says that the repeal of the ancient British navigation laws helped to turn British merchants to the screw steamer. They were unable to compete with the Americans in the use of sails, and had to take up the new ship or abandon the sea. The Cunard Company would have adopted iron ships promptly but for the contract with the Admiralty. The naval officers supposed that wooden walls were better for keeping out shot than iron, and it was not until 1855, as noted, that this company was allowed to use the best material. The fact that a subsidy thus restrained enterprise seems important here.
For a number of years the iron screw steamer had small effect upon the transatlantic trade. The owners of the sailing packets were making as much money as ever—perhaps more than ever, for they were building larger ships. In 1850, however, William Inman, an Englishman who had been interested in sailing ships, put on a line of iron screw packets between Liverpool and Philadelphia, as noted, and that line sealed the doom of the sailing packet. For the Collins, the Bremen, and the Cunard lines had taken, or were to take, only the cabin passengers and the express freight from the sailing packets, while Inman was after the steerage passengers and the coarser freight. The emigrants were all travelling from Europe to America. The greater part, in bulk, of the freight carried across the Atlantic travelled from America to Europe. Inman filled his ships with emigrants bound west, and with coarse freight bound east. Having a cargo both ways is a most important feature of successful navigation. Inman made money from the first voyage, and he did so without a penny of subsidy. The City of Manchester, of his line, made a net profit of 40 per cent the first year.
For the sake of emphasis let it be said that our transatlantic sailing packets lost their trade, not because the Cunard Company received a subsidy, and not because Collins lost the subsidy he had been receiving, but because of the evolution of a cargo carrier that was far more efficient than the American ship of the sail at its best. And the Collins and Bremen lines were beaten because they, too, were much less efficient than their competitors.
The reader may now ask why the American ship-owner did not adopt the iron screw steamer. A brief review of the conditions will answer the question. He could secure all the capital he needed for the well-tried sailing ship, but no one would advance money for what seemed to be, then, an experiment with a curious device not yet well tried out. Almost incredible as the statement may seem now, the most influential American ship-owners, during the years before the Civil War, refused to have anything to do with the screw propeller. In an essay on "Screw Propulsion in the United States," read before the American Society of Naval Architects and Marine Engineers, at a meeting held in New York in November, 1909, Mr. Charles H. Cramp, vice-president of the Society, said (see Shipping Illustrated, November 20, 1909):—
"The supremacy of British propulsion practically began with the advent of the fine screw steamship Great Britain in 1844, but New York interests would not consider any other than the paddle-wheel, with its walking-beam engine; and as they knew nothing of any other type, they loudly and persistently proclaimed its superiority over all other types, and carried with them the ship-owners, shipbuilders, shipping men, mariners, and all others in general, and the screw propeller was sneered at by them."