was imprisoned in default of payment of the royalty, and fine demanded. He died a disappointed and impoverished man. The plan thus unsuccessfully introduced by Hornblower was subsequently modified and adopted by others among the contemporaries of Watt; and, with higher steam and the use of the Watt condenser, the "compound" gradually became a standard type of steam-engine.

Arthur Woolf, in 1804, re-introduced the Hornblower or Falck engine, with its two steam-cylinders, using steam of higher tension. His first engine was built for a brewery in London, and a considerable number were subsequently made. Woolf expanded his steam from six to nine times, and the pumping-engines built from his plans were said to have raised about 40,000,000 pounds one foot high per bushel of coals, when the Watt engine was raising but little more than 30,000,000. In one case, a duty of 57,000,000 was claimed.

The most successful of those competitors of Watt who endeavored to devise a peculiar form of pumping-engine, which should have the efficiency of that of Boulton & Watt, and the necessary advantage in first cost, were WILLIAM BULL and RICHARD TREVITHICK.' The accompanying illustration shows the design, which was then known as the "Bull Cornish Engine."

The steam-cylinder, a, is carried on wooden beams, b, extending across the engine-house directly over the pumpwell. The piston-rod, c, is secured to the pump-rods, dd, the cylinder being inverted, and the pumps, e, in the shaft, f, are thus operated without the intervention of the beam invariably seen in Watt's engines. A connecting-rod, g, attached to the pump-rod and to the end of a balance-beam, h, operates the latter, and is counterbalanced by a weight, i. The rod, j, serves both as a plug-rod and as an air-pump connecting-rod. A snifting-valve, k, opens

For an exceedingly interesting and very faithful account of their work, see "Life of Richard Trevithick," by F. Trevithick, London, 1872.

when the engine is blown through, and relieves the condenser and air-pump, l, of all air. The rod, m, operates a

solid air-pump piston, the valves of the pump being placed on either side at the base, instead of in the pump-bucket, as

in Watt's engines. The condensing-water cistern was a wooden tank, n. A jet "pipe-condenser," o, was used instead of a jet condenser of the form adopted by other makers, and was supplied with water through the cock, p. The plug-rod, q, as it rises and falls with the pump-rods and balance-beam, operates the "gear-handles," rr, and opens and closes the valves, 88, at the required points in the stroke. The attendant works these valves by hand, in starting, from the floor, t. The operation of the engine is similar to that of a Watt engine. It is still in use, with a few modifications and improvements, and is a very economical and durable machine. It has not been as generally adopted, however, as it would probably have been had not the legal proscription of Watt's patents so seriously interfered with its introduction. Its simplicity and lightness are decided advantages, and its designers are entitled to great credit for their boldness and ingenuity, as displayed in their application of the minor devices which distinguish the engine. The design is probably to be credited to Bull originally; but Trevithick built some of these engines, and is supposed to have greatly improved them while working with Edward Bull, the son of the inventor, William Bull. One of these engines was erected by them at the Herland Mine, Cornwall, in 1798, which had a steam-cylinder 60 inches in diameter, and was built on the plan just described.

Another of the contemporaries of James Watt was a clergyman, EDWARD CARTWRIGHT, the distinguished inventor of the power-loom, and of the first machine ever used in combing wool, who revived Watt's plan of surface-condensation in a somewhat modified form. Watt had made a "pipe-condenser," similar in plan to those now often used, but had simply immersed it in a tank of water, instead of in a constantly-flowing stream. Cartwright proposed to use two concentric cylinders or spheres, between which the steam entered when exhausted from the cylinder of the en

gine, and was condensed by contact with the metal surfaces. Cold water within the smaller and surrounding the exterior vessel kept the metal cold, and absorbed the heat discharged by the condensing vapor.

Cartwright's engine is best described in the Philosophical Magazine of June, 1798, from which the accompanying sketch is copied.

FIG. 39.-Cartwright's Engine, 1798.

The object of the inventor is stated to have been to remedy the defects of the Watt engine-imperfect vacuum, friction, and complication.

In the figure, the steam-cylinder takes steam through the pipe, B. The piston, R, has a rod extending downward to the smaller pump-piston, G, and upward to the cross-head, which, in turn, drives the cranks above, by means of connecting-rods. The shafts thus turned are con

nected by a pair of gears, ML, of which one drives a pinion on the shaft of the fly-wheel. D is the exhaustpipe leading to the condenser, F; and the pump, G, removes the air and water of condensation, forcing it into the hot-well, H, whence it is returned to the boiler through the pipe, I. A float in H adjusts an air-valve, so as to keep a supply of air in the chamber, to serve as a cushion and to make an air-chamber of the reservoir, and permits the excess to escape. The large tank contains the water supplied for condensing the steam.

The piston, R, is made of metal, and is packed with two sets of cut metal rings, forced out against the sides of the cylinder by steel springs, the rings being cut at three points in the circumference, and kept in place by the springs. The arrangement of the two cranks, with their shafts and gears, is intended to supersede Watt's plan for securing a perfectly rectilinear movement of the head of the pistonrod, without friction.

In the accounts given of this engine, great stress is laid upon the supposed important advantage here offered, by the introduction of the surface-condenser, of permitting the employment of a working-fluid other than steam-as, for example, alcohol, which is too valuable to be lost. It was proposed to use the engine in connection with a still, and thus to effect great economy by making the fuel do double duty. The only part of the plan which proved both novel and valuable was the metallic packing and piston, which has not yet been superseded. The engine itself never came

into use.

At this point, the history of the steam-engine becomes the story of its applications in several different directions, the most important of which are the raising of waterwhich had hitherto been its only application-the locomotive-engine, the driving of mill-machinery, and steam-navigation.

Here we take leave of James Watt and of his contempo