CHAP. II.]

WATT'S PROPOSED LOCOMOTIVE.

65

Though Watt repeatedly expressed his intention of constracting a model locomotive after his specification, it does not appear that he ever carried it out. He was too much engrossed with other work; and, besides, he never entertained very sanguine views as to the practicability of road locomotion by steam. He continued, however, to discuss the subject with his partner Boulton, and from his letters we gather that his mind continued undetermined as to the best plan to be pursued. Only four days after the date of the above specification (i. e., on the 28th of August, 1784) we find him communicating his views on the subject to Boulton at great length, and explaining his ideas as to how the proposed object might best be accomplished. He first addressed himself to the point of whether 80 lbs. was a sufficient power to move a post-chaise on a tolerably good and level road at four miles an hour; secondly, whether 8 ft. of boiler surface exposed to the fire would be sufficient to evaporate a cube foot of water per hour without much waste of fuel; thirdly, whether it would require steam of more than eleven and a half times atmospheric density to cause the engine to exert a power equal to 6 lbs. on the inch. "I think," he observed, "the cylinder must either be made larger or make more than sixty strokes per minute. As to working gear, stopping and backing, with steering the carriage, I think these things perfectly manageable."

"My original ideas on the subject,” he continued, "were prior to my invention of these improved engines, or before the crank, or any other of the rotative motions were thought of. My plan then was to have two inverted cylinders, with toothed racks instead of piston-rods, which were to be applied to two ratchet-wheels on the axle-tree, and to act alternately; and I am partly of opinion that this method might be applied with advantage yet, because it needs no fly and has some other conveniences. From what I have said, and from much more which a little reflection will suggest to you, you will see that without several circumstances turn out more favorable than has been stated, the machine will be clumsy and defective, and that it will cost much time to bring it to any tolerable degree of perfection, and that for me to interrupt the career of our business would be imprudent; I even grudge the time I have taken to make these comments on it. There is, however, another way in which much mechanism might be saved if it be in itself practicable, which is to apply to it one of the self-moving rotatives, which has no regula

E

tors, but turns like a mill-wheel by the constant influx and efflux of steam; but this would not abridge the size of the boiler, and I am not sure that such engines are practicable."

It will be observed from these explanations that Watt's views as to road locomotion were still crude and undefined; and, indeed, he never carried them farther. While he was thus discussing the subject with Boulton, William Murdock, one of the most skilled and ingenious workmen of the Soho firm-then living at Redruth, in Cornwall-was occupying himself during his leisure hours, which were but few, in constructing a model locomotive after a design of his own. He had doubtless heard of the proposal to apply steam to locomotion, and, being a clever inventor, he forthwith set himself to work out the problem. The plan he pursued was very simple and yet efficient. His model was of small dimensions, standing little more than a foot high, but it was sufficiently large to demonstrate the soundness of the principle on which it was constructed. It was supported on three wheels, and

SECTION OF MURDOCK'S MODEL.

carried a small copper boiler, heated by a spirit-lamp, with a flue passing obliquely through it. The cylinder, ofin. diameter and 2 in. stroke, was fixed in the top of the boiler, the piston-rod being connected with the vibrating beam attached to the connecting-rod which worked the crank of the drivingwheel. This little engine worked

by the expansive force of the steam only, which was discharged into the atmosphere after it had done its work of alternately raising and depressing the piston in the cylinder.

Mr. Murdock's son informed the author that this model was invented and constructed in 1781, but, from the correspondence of Boulton and Watt, we infer that it was not ready for trial until 1784. The first experiment with it was made in Murdock's own house at Redruth, when it successfully hauled a model wagon round the room-the single wheel placed in front of the engine, and working in a swivel frame, enabling it to run round in a circle.

Another experiment was made out of doors, on which occasion,

CHAP. II.]

MURDOCK'S MODEL ENGINE.

67

small though the engine was, it fairly outran the speed of its inventor. It seems that one night, after returning from his duties at the Redruth mine, Murdock determined to try the working of his model locomotive. For this purpose he had recourse to the walk leading to the church, about a mile from the town. It was rather narrow, and was bounded on each side by high hedges. The night was dark, and Murdock set out alone to try his experiment. Having lit his lamp, the water soon boiled, when off started the engine, with the inventor after it. Shortly after he heard distant shouts of terror. It was too dark to perceive objects; but he found, on following up the machine, that the cries proceeded from the worthy pastor of the parish, who, going toward the town, was met on this lonely road by the hissing and fiery little monster, which he subsequently declared he had taken to be the Evil One in propria persona!

Watt was by no means pleased when he learned that Murdock was giving his mind to these experiments. He feared that it might have the effect of withdrawing him from the employment of the firm, to which his services had become almost indispensable; for there was no more active, skillful, or ingenious workman in all their concern. Watt accordingly wrote to Boulton, recommending him to advise Murdock to give up his locomotive-engine scheme; but, if he could not succeed in that, then, rather than lose Murdock's services, Watt proposed that he should be allowed an advance of £100 to enable him to prosecute his experiments, and if he succeeded within a year in making an engine capable of drawing a post-chaise carrying two passengers and the driver at four miles an hour, it was suggested that he should be taken as partner into the locomotive business, for which Boulton and Watt were to provide the necessary capital.

Two years later (in September, 1786) we find Watt again expressing his regret to Boulton that Murdock was "busying himself with the steam-carriage." "I have still," said he," the same opinion concerning it that I had, but to prevent as much as possible more fruitless argument about it, I have one of some size under hand, and am resolved to try if God will work a miracle in favor of these carriages. I shall in some future letter send you the words of my specification on that subject. In the mean time I wish William could be brought to do as we do, to mind

the business in hand, and let such as Symington and Sadler throw away their time and money in hunting shadows." In a subsequent letter Watt expressed his gratification at finding "that William applies to his business." From that time Murdock as well as Watt dropped all farther speculation on the subject, and left it to others to work out the problem of the locomotive engine. Murdock's model remained but a curious toy, which he himself took pleasure in exhibiting to his intimate friends; and though he long continued to speculate about road locomotion, and was persuaded of its practicability, he refrained from embodying his ideas of it in any more complete working form.

Symington and Sadler, the "hunters of shadows" referred to by Watt, did little to advance the question. Of Sadler we know nothing beyond that in 1786 he was making experiments as to the application of steam-power to the driving of wheel-carriages. This came to the knowledge of Boulton and Watt, who gave him notice, on the 4th of July of the same year, that "the sole privilege of making steam-engines by the elastic force of steam acting on a piston, with or without condensation, had been granted to Mr. Watt by Act of Parliament, and also that among other improvements and applications of his principle he hath particularly specified the application of steam-engines for driving wheel carriages in a patent which he took out in the year 1784." They accordingly cautioned him against proceeding farther in the matter; and as we hear no more of Sadler's steam-carriage, it is probable that the notice had its effect.

The name of William Symington is better known in connection with the history of steam locomotion by sea. He was born at Leadhills, in Scotland, in 1763. His father was a practical mechanic, who superintended the engines and machinery of the Mining Company at Wanlockhead, where one of Boulton and Watt's pumping-engines was at work. Young Symington was of an ingenious turn of mind from his boyhood, and at an early period he seems to have conceived the idea of employing the steam-engine to drive wheel-carriages. His father and he worked together, and by the year 1786, when the son was only twentythree years of age, they succeeded in completing a working model of a road locomotive. Mr. Meason, the manager of the mine, was so much pleased with the model, the merit of which princi

CHAP. II.]

SYMINGTON'S STEAM-CARRIAGE.

69

pally belonged to young Symington, that he sent him to Edinburg for the purpose of exhibiting it before the scientific gentlemen of that city, in the hope that it might lead, in some way, to his future advancement in life. Mr. Meason also allowed the model to be exhibited at his own house there, and he invited many gentlemen of distinction to inspect it.

The machine consisted of a carriage and locomotive behind, supported on four wheels. The boiler was cylindrical, communicating by a steam-pipe with the two horizontal cylinders, one on each side of the engine. When the piston was raised by the action of the steam, a vacuum was produced by the condensation of the steam in a cold-water tank placed underneath the engine, on which the piston was again forced back by the pressure of the atmosphere. The motion was communicated to the wheels by rack-rods connected with the piston-rod, which worked on each side of a drum fixed on the hind axle, the alternate action of which rods upon the tooth and ratchet wheels with which the drum was provided producing the rotary motion. It will thus be observed that Symington's engine was partly atmospheric and partly condensing, the condensation being effected by a separate vessel and air-pump, as patented by Watt; and though the arrangement was ingenious, it is clear that, had it ever been brought into use, the traction by means of such an engine would have been of the very slowest kind.

But Symington's engine was not destined to be applied to road locomotion. He was completely diverted from employing it for