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, 7, as it rises and falls with the pump-rods and balance-beam, operates the "gear-handles," rr, and opens and closes the valves, ss, 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

raries, of the former of whom a French author' says: "The part which he played in the mechanical applications of the power of steam can only be compared to that of Newton in astronomy and of Shakespeare in poetry." Since the time. of Watt, improvements have been made principally in matters of mere detail, and in the extension of the range of application of the steam-engine.2

1 Bataille, "Traité des Machines à Vapeur," Paris, 1847.

2 See "Stationary Engines for Electric Lighting," New York, 1884, "Manual of Steam-Engines," New York, 1890, by the author, for more formal discussion,

CHAPTER IV.

THE MODERN STEAM-ENGINE.

"THOSE projects which abridge distance have donc most for the civilization and happiness of our species."-MACAULAY.

THE SECOND PERIOD OF APPLICATION-1800-240. STEAM-LOCOMOTION ON RAILROADS.

INTRODUCTORY.-The commencement of the nineteenth century found the modern steam-engine fully developed in

all its principal features, and fairly at work in many departments of industry. The genius of Worcester, and Morland, and Savery, and Desaguliers, had, in the first period of the