The Advent of the Screw Propeller
But by this time the success of the Atlantic steamship was , and in December, 1839, the President, a craft of 2,3G6 tons and 540 horse power, was launched. Curling & Young built her on the Thames, but in March 1841, on the return trip from New York, she was lost with all aboard. In 1840, the Great Western Company undertook a step of vast importance. The chief marine architect and engineer of that time was Isambard K. Brunel.
When the Great Western Company applied to him for a vessel that would eclipse any craft afloat, he advised the building of an iron ship of three thousand tons. His plans were carried out in the Great Britain, a craft of fine model, for whose construction a special graving dock was built. Brunel's first designs were for a side-wheeler, but were changed while the hull was building.
At this time, marine engineers were experimenting with the screw as a substitute for the expensive, cumbersome, and otherwise inefficient paddlewheels of that day. As early as 1770, it had been suggested by Watt, and nine years later one Matthew Wasborough, of Bristol, is said to have taken out a patent on such a device. Its efficiency was first really proved by Stevens, in 1804, and but for the failure of his engines his work would have helped the world in a great stride towards progress. It was left to Ericsson, however, to perfect the new propeller in 1836, during his residence in England.
Following his suggestions, Thomas Petit Smith, an English engineer, built a screw steamship in 1839 that was a complete success. The vessel was a hundred and twenty five feet long, twenty-two beam, and thirteen deep, and named .the Archimedes. It chanced that he took this vessel to Bristol in 1842, when Brunel, at once recognizing its advantages, changed the Great Britain's plans, and introduced the screw in place of the paddlewheels.
The engines were of 1,500 I. H. P. (indicated horsepower) and of such unusual size that the company itself was compelled to build them. It is said, furthermore, that Nasmyth invented the steam hammer in order to forge her main shaft. The engines had four cylinders of eighty-eight inches diameter; she was three hundred and twenty two feet long, and fifty-one feet wide.
A curious feature of her machinery was that four endless chains drove the screw shaft over a large drum. Compared with the prevailing type, the Great Britain was a great success, but she ran on the Atlantic route only three seasons. Then, after going ashore in Dundrum Bay, Ireland, she was hauled off, refitted with direct acting engines of five hundred horsepower, and entered in the Melbourne trade. She is now said to be a coal hulk in the Falkland Islands.
Notwithstanding the success of the Great Britain, the prejudice against iron hulls and the screw was difficult to overcome. Navigators declared it unsafe to venture in hulks whose metal destroyed the usefulness of the compass, and the iron's disposition to foul rapidly was another serious defect. But subsequently both these evils were overcome by the introduction of the floating compass and of the anti fouling compositions for painting ship's bottoms. Later, when marine engineers obtained fixed scientific knowledge concerning the screw propeller, its slight defects were remedied; and with the construction of direct acting engines, its success was assured.