A History of the Growth of the Steam-Engine

by Robert Henry Thurston

The now familiar “Stevens cut-off,” a peculiar device for securing the expansion of steam in the steam-cylinder, was the invention (1841) of Robert L. Stevens and a nephew, who inherited the same constructive talent which distinguished the first of these great men—Mr. Francis B. Stevens. In this form of valve-gear, the steam and exhaust valves are independently worked by separate eccentrics, the latter being set in the usual manner, opening and closing the exhaust-passages just before the crank passes its centre. The steam-eccentric is so placed that the steam-valve is opened as usual, but closed when but about one-half the stroke has been made. This result is accomplished by giving the eccentric a greater throw than is required by the motion of the valve, and permitting it to move through a portion of its path without moving the valve. Thus, in [Fig. 90], if A B be the direction of motion of the eccentric-rod, the valve would ordinarily open the steam-port when the eccentric assumes the position O C, closing when the eccentric has passed around to O D. With the Stevens valve-gear, the valve is opened when the eccentric reaches O E, and closes when it arrives at O F. The steam-valve of the opposite end of the cylinder is open while the eccentric is moving from O M to O K. Between K and E, and between F and M, both valves are seated. H B is proportional to the lift of the valve, and O H to the motion of the valve-gear when out of contact with the valve-lifters. While the crank is moving through an arc, E F, steam is entering the cylinder; from F to M the steam is expanding. At M the stroke is completed, and the other steam-valve opens. The ratio E M∕E L is the ratio of expansion.

This form of cut-off motion is still a very usual one, and can be seen in nearly all steamers in the United States not using the device of Sickles. It was at about this time, also, that Stevens, having succeeded his father in the business of introducing the steam-engine in land-transportation, as well as on the water, adopted the use of steam expansively on the locomotives of the Camden & Amboy Railroad, which was controlled and built by capital furnished principally by the Messrs. Stevens. He at the same time constructed eight-wheeled engines for heavy work, and adopted anthracite coal as fuel. In the latter change he was thoroughly successful, and the same improvement was made with engines built for fast traffic in 1848.

The most remarkable of all the applications of steam-power proposed by Robert L. Stevens was that known as the Stevens Steam Iron-Clad Battery. As has already been stated, Colonel John Stevens had proposed, as early as 1812, to build a circular or saucer-shaped iron-clad, like those built 60 years later for the Russian Navy. Nothing was done, however, although the son revived the idea in a modified form 20 years afterward. In the years 1813-’14, the war with England being then in progress, he invented, after numerous and hazardous experiments, an elongated shell, to be fired from ordinary smooth-bored cannon. Having perfected this invention, he sold the secret to the United States, after making experiments to prove their destructiveness so decisive as to leave no doubt of the efficacy of such projectiles.

As early as 1837 he had perfected a plan of an iron-clad war-vessel, and in August, 1841, his brothers, James C. and Edwin A. Stevens, representing Robert L., addressed a letter to the Secretary of the Navy, proposing to build an iron-clad vessel of high speed, with all its machinery below the water-line, and having submerged screw-propellers. The armament was to consist of the most powerful rifled guns, loading at the breech, and provided with elongated shot and shell. In the year 1842, having contracted to build for the United States Government a large war-steamer on this plan, which should be shot and shell proof, Robert L. Stevens built a steamboat at Bordentown, for the sole purpose of experimenting on the forms and curves of propeller-blades, as compared with side-wheels, and continued his experiments for many months. After some delay, during which Mr. Stevens and his brothers were engaged with their experiments and in perfecting their plans, the keel of an iron-clad was laid down in a dry-dock which had been constructed for the purpose at great cost. This vessel was to have been 250 feet long, of 40 feet beam, and 28 feet deep. The machinery was designed to furnish 700 indicated horse-power. The plating was proposed to be 41∕2 inches thick—the same thickness of armor as was adopted 10 years later by the French for their comparatively rude constructions.

In 1854, such marked progress had been made in the construction of ordnance that Mr. Stevens was no longer willing to proceed with the original plans, fearing that, were the ship completed, it might prove not invulnerable, and might throw some discredit upon its designer, as well as upon the navy of which it was to form a part. The work, which had, in those years of peace, progressed very slowly and intermittently, was therefore stopped entirely, the vessel given up, and in 1854 the keel of a ship of vastly greater size and power was laid down. The new design was 415 feet long, of 45 feet beam, and of something over 5,000 tons displacement. The thickness of armor proposed was 63∕4 inches—21∕4 inches thicker than that of the first French and British iron-clads—and the machinery was designed by Mr. Stevens to be of 8,624 indicated horse-power, driving twin-screws, and propelling the vessel 20 miles or more an hour. As with the preceding design, the progress of construction was intermittent and very slow. Government advanced funds, and then refused to continue the work; successive administrations alternately encouraged and discouraged the engineer; and he finally, cutting loose entirely from all official connections, went on with the work at his own expense.

The remarkable genius of the elder Stevens was well reflected in the character of his son, and is in no way better exemplified than by the accuracy with which, in this great ship, those forms and proportions, both of hull and machinery, were adopted which are now, twenty-five years later, recognized as most correct under similar conditions. The lines of the vessel are beautifully fair and fine, and are what J. Scott Russell has called “wave-lines,” or trochoidal lines, such as Rankine has shown to be the best possible for easy propulsion. The proportion of length to midship dimensions is such as to secure the speed proposed with a minimum resistance, and to accord closely with the proportions arrived at and adopted by common consent in present transoceanic navigation by the best—not to say radical—builders.

The death of Robert L. Stevens occurred in April, 1856, when this larger vessel had advanced so far toward completion that the hull and machinery were practically finished, and it only remained to add the armor-plating, and to decide upon the form of fighting-house and upon the number and size of guns. The construction of the vessel, which had proceeded slowly and intermittently during the years of peace, as successive administrations had considered it necessary to continue the payment of appropriations, or had stopped temporarily in the absence of any apparent immediate necessity for continuance of the work, was again interrupted by his death.

The name of Robert L. Stevens will be long remembered as that of one of the greatest of American mechanics, the most intelligent of naval architects, and as the first, and one of the greatest, of those to whom we are indebted for the commencement of the mightiest of revolutions in the methods and implements of modern naval warfare. American mechanical genius and engineering skill have rarely been too promptly recognized, and no excuse will be required for an attempt (which it is hoped may yet be made) to place such splendid work as that of the Messrs. Stevens in a light which shall reveal both its variety and extent and its immense importance.

While Fulton was introducing the steamboat upon the waters of New York Bay and the Hudson River, and while the Stevenses, father and sons, were rapidly bringing out a fleet of steamers on the Delaware River and Bay, other mechanics were preparing to contest the field with them as opportunity offered, and as legislative acts authorizing monopoly expired by limitation or were repealed.

About 1821, Robert L. Thurston, John Babcock, and Captain Stephen T. Northam, of Newport, R. I., commenced building steamboats, beginning with a small craft intended for use at Slade’s Ferry, on an arm of Narragansett Bay, near Fall River. They afterward built vessels to ply on Long Island Sound. One of their earliest boats was the Babcock, built at Newport in 1826. The engine was built by Thurston and Babcock, at Portsmouth, R. I. They were assisted in their work by Richard Sanford, and with funds by Northam. The engine was of 10 or 12 inches diameter of cylinder, and 3 or 4 feet stroke of piston. The boiler was a form of “pipe-boiler,” subsequently (1824) patented by Babcock. The water used was injected into the hot boiler as fast as required to furnish steam, no water being retained in the steam-generator. This boat was succeeded, in 1827-’28, by a larger vessel, the Rushlight, for which the engine was built by James P. Allaire, at New York, while the boat was built at Newport. The boilers of both vessels had tubes of cast-iron. The smaller of these boats was of 80 tons burden; it steamed from Newport to Providence, 30 miles, in 31∕2 hours, and to New York, a distance of 175 miles, in 25 hours, using 13∕4 cord of wood.[82] Thurston and Babcock subsequently removed to Providence, where the latter soon died. Thurston continued to build steam-engines at this place until nearly a half-century later, dying in 1874.[83] The establishment founded by him, after various changes, became the Providence Steam-Engine Works.