History of merchant shipping and ancient commerce, Volume 4 (of 4)

by W. S. Lindsay

Like the boatmen of the Nile, the men who make these wooden habitations their usual dwellings are a distinct class. Launching their boats upon the Ohio, the Illinois, the Upper Mississippi, the Missouri, the Arkansas, and the Cumberland with all their respective tributaries, and guiding them to their final resting-place at New Orleans, these men are all known by the general designation of “Boatmen of the Mississippi.” They are a strong, hardy, rough, uncouth people, with a touch of the savage about them.

Engines.

Although the condensing engine is met with in some of the Mississippi steamers, high pressure engines are much more frequent, the pressure in the former being never less than 10 and frequently as high as 30 pounds to the square inch; when, however, this pressure is so worked, the object is to shut off the steam and take advantage of the expansion. In high pressure engines the pressure is used ad libitum from 50 to 150 pounds, and, in former times, to such an extent, that no mortal was left to measure its height, the boiler as well as the boat and its contents, animate and inanimate, having too frequently been blown into the air. In condensing engines, when moving at full speed, the steam is never “wire-drawn,” as the engineers term it, the passages being made large enough, and the valves fully opened: the same, in high pressure engines: but, when not moving at full speed, the steam can be “wire-drawn” as the engineer thinks necessary.

The term “high pressure” in America is applied to that description of engine which is worked against the atmosphere or without condensation; all condensing engines are called low pressure. In both these engines ashwood and pine, where coal could not be easily obtained, were the descriptions of wood most commonly used for fuel,[155] and, in the dangerous competition, happily less frequent now than it was some years ago, barrels of pitch, rosin, and even tallow were sometimes thrown into the furnaces, the recklessness of the captains and engineers on the Mississippi in working their boilers at a greater pressure than they could with safety carry, and, thereby, causing the frightful explosions to which I have just referred.[156]

Different construction of the steamers on the Atlantic rivers.

The steam-boats on the Atlantic rivers are differently constructed from those of the west, as the same necessity for light draught of water does not exist, while they are more especially intended for passengers; their cabins are, frequently, under deck, while those on the western rivers, constructed for carrying heavy cargoes as well as passengers, have their cabins, generally, in two tiers above the deck, hence the preference given to high pressure engines from their being lighter and occupying less space. The condensing or low pressure engine is much more prevalent in the Eastern boats, and is more economical in fuel than the high pressure: their boilers are usually circular; there is great variety in the form and construction of the furnaces and flues, and the boilers designed for burning wood are, of necessity, of greater external dimensions than those designed for burning coal, although the proportions of steam space may be smaller in the former than in the latter. These boilers are frequently worked at 18 to 20 pounds on the square inch, but 12 pounds is considered the medium.

The expansive action of the superheated steam in these engines, the greater space allowed for the engines to work in, and the generally admirable form of the boats, will, of course, tend to reduce the quantity of fuel required. The stroke of the piston, in some of the fastest American boats, is as much as 10 or 11 feet, and the connecting rods 13 to 19 feet long: the engine is worked at a much quicker rate than in England, the piston passing through the space of 500 feet in a minute, at which speed the whole machinery is found to work more smoothly than at a slower rate. It has been remarked by competent judges that, though the English engine is more perfect and more highly finished than the American, the advantage of superior workmanship is more than compensated in the American by greater length of stroke and the connection. American engineers consider the English engine, as applied to marine purposes, too confined, and until steam of a higher pressure is used, the boat must be of inferior speed to those of the United States. A Boulton and Watt engine[157] of 30-inch cylinder and 4-foot stroke, making twenty-five revolutions in a minute with 3½ pounds of steam, is estimated as a 30-horse engine; but the force of this engine, it is argued by Americans, will be increased one-third if steam of 7 pounds be used; “lengthen the cylinder,” they remark, to 8 feet and drive the piston through that space in the same time, that is, 400 feet instead of 200, use the same quantity of steam by shutting it off at half the stroke, and the American engine as compared with the English will be nearly an 80-horse instead of a 30-horse power.

Great speed of American lake and river steamers.

In their early career the Americans were likewise much in advance, as we have seen, of Great Britain in the model and speed of their river steamers, a superiority they still maintain. Indeed, the competition on their rivers, especially on the Hudson, was then much greater than it is even now. This strong rivalry made speed of the utmost importance, as the boat which performed the trip between New York and Albany in the shortest time, if only by half an hour (the Americans not concerning themselves about the chance of an explosion), would be sure to take all the passengers. Hence every expedient ingenuity could devise was resorted to for this object, and to the skill and perseverance of Mr. Robert L. Stevens the Americans are greatly indebted for the perfection to which the models of their river boats have advanced. These boats were built on the finest models; their entrance and runs sharper than had ever been before attempted; besides this, he had several of the earlier ones sawn in two and their length increased 25 or 30 feet, at the same time carrying a false bow from 18 to 20 feet beyond the stem, and forming true lines with the planking of the boat. This experiment fully answered his expectations; their speed was surprisingly increased, and, when running at the rate of 18 miles an hour, “they hardly raised a feather in front.” But, in 1834, another American shipbuilder constructed a steamer 185 feet long and 20 feet beam, with solid ends sharper than any of the false bows, having a flat floor and a single-cylinder engine of 52-inch diameter and 10-feet stroke, which was pronounced to be “the fastest thing afloat:” indeed, to such perfection have these steamers been brought that they now traverse rivers once thought to be altogether unnavigable. The first attempt to reach the falls of the Ohio from New Orleans was considered so visionary that the projector was looked upon as little better than a madman, but steamers are now engaged in regular traffic wherever the bars are covered with 12 or 15 inches of water, American genius, skill, and perseverance having triumphed over almost every impediment.

Peculiarity of construction.