The river Hudson rises near Lake Champlain, the easternmost of the great chain of lakes or inland seas which extend from east to west across the northern boundary of the United States. The river follows nearly a straight course southwards for two hundred and fifty miles, and empties itself into the sea at New York. The influence of the tide is felt as far as Albany, above which the stream begins to contract. Although this river in magnitude and extent is by no means equal to several others which intersect the States, it is nevertheless rendered an object of great interest by reason of the importance and extent of its trade. The produce of the state of New York and that of the banks of the great Lakes Ontario and Erie are transported by it to the capital; and one of the most extensive and populous districts of the United States is supplied with the necessary imports by its waters. A large fleet of vessels is constantly engaged in its navigation; nor is the tardy but picturesque sailing vessel as yet excluded by the more rapid steamers. The current of the Hudson is said to average nearly three miles an hour; but as the ebb and flow of the tide are felt as far as Albany, the passage of the steamers between that place and New York may be regarded as equally affected by currents in both directions, or nearly so. The passage therefore, whether in ascending or descending the river, is made nearly in the same time.
(231.)
The position and form of the machinery is likewise affected by these conditions. Without the necessity of being protected from a rough sea, it is placed on the deck in an elevated position. The cylinders of large diameter and short stroke invariably used in Europe are unknown in America, and the proportions are reversed, a small diameter and stroke of great length being invariably adopted. It is rarely that two engines are used. A single engine, placed in the centre of the deck, with a cylinder from forty to sixty inches' diameter, and from eight to ten foot stroke, drives paddle-wheels from twenty-one to twenty-five feet in diameter, producing from twenty-five to thirty revolutions per minute. The great magnitude of the paddle-wheels and the velocity imparted to them enable them to perform the office of fly-wheels, and to carry the engine round its centres, not however without a perceptible inequality of motion, which gives to the American steamer an effect like that of a row boat advancing by starts with each stroke of the piston. The length of stroke adopted in these engines enables them to apply with great effect the expansive principle, which is almost universally used, the steam being generally cut off at half stroke.
The steamers which navigate the Hudson are vessels of considerable magnitude, splendidly fitted up for the accommodation of passengers; they vary from one hundred and eighty to two hundred and forty feet in length, and from twenty to thirty feet in width of beam. In the following table is given the particulars of nine steamers plying on this river, taken from [Pg494] the work of Mr. Stevenson, and from the paper of Mr. Renwick, inserted in the last edition of Tredgold:—
| Names. | Length of Deck. | Breadth of Beam. | Draft of Water. | Drain of Wheel. |
|---|---|---|---|---|
| Ft. | Ft. | Ft. | Ft. | |
| Dewit Clinton | 230 | 28 | 5·5 | 21 |
| Champlain | 180 | 27 | 5·5 | 22 |
| Erie | 180 | 27 | 5·5 | 22 |
| North America | 200 | 30 | 5 | 21 |
| Independence | 148 | 26 | -- | -- |
| Albany | 212 | 26 | -- | 24·5 |
| Swallow | 233 | 22·5 | 3·75 | 24 |
| Rochester | 200 | 25 | 3·75 | 23·5 |
| Utica | 200 | 21 | 3·5 | 22 |
| Names. | Length of Paddles. | Depth of Paddles. | Number of Engines. | Drain of Cylinder. |
|---|---|---|---|---|
| Ft. | In. | In. | ||
| Dewit Clinton | 13·7 | 36 | 1 | 65 |
| Champlain | 15 | 34 | 2 | 44 |
| Erie | 15 | 34 | 2 | 44 |
| North America | 13 | 30 | 2 | 44·5 |
| Independence | -- | -- | 1 | 44 |
| Albany | 14 | 30 | 1 | 65 |
| Swallow | 11 | 30 | 1 | 46 |
| Rochester | 10 | 24 | 1 | 43 |
| Utica | 9·5 | 24 | 1 | 39 |
| Names. | Length of Stroke. | Number of Rev. | Part of Stroke at which it is cut off. |
|---|---|---|---|
| Ft. | |||
| Dewit Clinton | 10 | 29 | 3⁄4 |
| Champlain | 10 | 27·5 | 1⁄2 |
| Erie | 10 | 27·5 | 1⁄2 |
| North America | 8 | 24 | 1⁄2 |
| Independence | 10 | ||
| Albany | -- | 19 | |
| Swallow | -- | 27 | |
| Rochester | 10 | 28 | |
| Utica | 10 |
None of these vessels have either masts or rigging, and consequently never derive any propelling power except from the engines: they are neither manned nor commanded by persons having any knowledge of navigation: the works that are visible above their decks are the beam and framing of the engine, and the chimneys.
The engines used for steamers on the Hudson, and other great rivers and bays on the eastern coast of America, are most commonly condensing engines, but they nevertheless work with steam of very high pressure, being seldom less than twenty-five pounds per square inch, and sometimes as much as fifty. By reference to the preceding table it will be seen, that the velocity of the piston greatly exceeds the limit generally observed in Europe. It is customary in European marine engines to limit the speed of the piston to about two hundred and twenty feet per minute. Even the piston of a locomotive engine does not much exceed the rate of three hundred feet per minute. In the American steamers, however, the pistons commonly move at the rate of from five to six hundred feet per minute, while the circumference of the paddle-wheels are driven at the rate of from twenty to twenty-two miles an hour. [Pg495]