engine to locomotion, and contemplated using either a noncondensing engine or an air-surface condenser. He actually included the locomotive-engine in his patent of 1784; and his assistant, Murdoch, in the same year, made a workingmodel locomotive (Fig. 45), which was capable of running at a rapid rate. This model, now deposited in the Patent Museum at South Kensington, London, had a flue-boiler, and its steam-cylinder was three-fourths of an inch in diameter, and the stroke of piston 2 inches. The driving-wheels were 9 inches diameter.

Nothing was, however, done on a larger scale by either Watt or Murdoch, who both found more than enough to claim their attention in the construction and introduction of other engines. Murdoch's model is said to have run from 6 to 8 miles an hour, its little driving-wheels making from 200 to 275 revolutions per minute. As is seen in the sketch, this model was fitted with the same form of engine, known as the "grasshopper-engine," which was used in the United States by Oliver Evans.

"To Oliver Evans," says Dr. Ernest Alban, the distinguished German engineer, "was it reserved to show the true value of a long-known principle, and to establish thereon a new and more simple method of applying the power of steam-a method that will remain an eternal memorial to

its introducer." Dr. Alban here refers to the earliest permanently successful introduction of the non-condensing high-pressure steam-engine.

OLIVER EVANS, one of the most ingenious mechanics that America has ever produced, was born at Newport, Del., in 1755 or 1756, the son of people in very humble circumstances.

He was, in his youth, apprenticed to a wheelwright, and soon exhibited great mechanical talent and a strong desire to acquire knowledge. His attention was, at an early period, drawn to the possible application of the power of steam to useful purposes by the boyish pranks of one of his comrades, who, placing a small quantity of water in a gunbarrel, and ramming down a tight wad, put the barrel in the fire of a blacksmith's forge. The loud report which

accompanied the expulsion of the wad was an evidence to young Evans of great and (as he supposed) previously undiscovered power.

Subsequently meeting with a description of a Newcomen engine, he at once noticed that the elastic force of confined steam was not there utilized. He then designed the noncondensing engine, in which the power was derived exclusively from the tension of high-pressure steam, and proposed its application to the propulsion of carriages.

About the year 1780, Evans joined his brothers, who were millers by occupation, and at once employed his inventive talent in improving the details of mill-work, and with such success as to reduce the cost of attendance onehalf, and also to increase the fineness of the flour made. He proved himself a very expert millwright.

In 1786 he applied to the Pennsylvania Legislature for a patent for the application of the steam-engine to driving mills, and to the steam-carriage, but was refused it. In 1800 or 1801, Evans, after consultation with Professor Robert Patterson, of the University of Pennsylvania, and getting his approval of the plans, commenced the construction of a steam-carriage to be driven by a non-condensing engine. He soon concluded, however, that it would be a better scheme, pecuniarily, to adapt his engine, which was novel in form and of small first cost, to driving mills; and he accordingly changed his plans, and built an engine of 6 inches diameter of cylinder and 18 inches stroke of piston, which he applied with perfect success to driving a plaster-mill.

This engine, which he called the "Columbian Engine," was of a peculiar form, as seen in Fig. 46. The beam is supported at one end by a rocking column; at the other, it is attached directly to the piston-rod, while the crank lies beneath the beam, the connecting-rod, 1, being attached to the latter at the extreme end. The head of the piston-rod is compelled to rise and fall in a vertical line by the "Evans's

parallelogram"-a kind of parallel-motion very similar to one of those designed by Watt. In the sketch (Fig. 46), 2 is the crank, 3 the valve-motion, 4 the steam-pipe from the boiler, E, 567 the feed-pipe leading from the pump, F A is the boiler. The flame from the fire on the grate, H, passes under the boiler between brick walls, and back through a central flue to the chimney, I.

Subsequently, Evans continued to extend the applications of his engine and to perfect its details; and, others following in his track, the non-condensing engine is to-day fulfilling the predictions which he made 70 years ago, when he said:

"I have no doubt that my engines will propel boats against the current of the Mississippi, and wagons on turnpike roads, with great profit. . . ."

"The time will come when people will travel in stages moved by steam-engines from one city to another, almost as fast as birds can fly, 15 or 20 miles an hour. . . . A carriage will start from Washington in the morning, the passengers will breakfast at Baltimore, dine at Philadelphia, and sup in New York the same day. . .

"Engines will drive boats 10 or 12 miles an hour, and

there will be hundreds of steamers running on the Mississippi, as predicted years ago."1

In 1804, Evans applied one of his engines in the transportation of a large flat-bottomed craft, built on an order of the Board of Health of Philadelphia, for use in clearing some of the docks along the water-front of the city. Mounting it on wheels, he placed in it one of his 5-horse power engines, and named the odd machine (Fig. 47) "Oruktor Amphibolis." This steam dredging-machine, weighing about 40,000 pounds, was then propelled very slowly from the works, up Market Street, around to the Water-Works, and

then launched into the Schuylkill. The engine was then applied to the paddle-wheel at the stern, and drove the craft down the river to its confluence with the Delaware.

In September of the same year, Evans laid before the Lancaster Turnpike Company a statement of the estimated expenses and profits of steam-transportation on the common road, assuming the size of the carriage used to be sufficient for transporting 100 barrels of flour 50 miles in 24 hours,

1 Evans's prediction is less remarkable than that of Darwin, elsewhere quoted.