The application of steam-power to the driving of wheel-carriages on common roads was in 1759 brought under the notice of James Watt by his young friend John Robison, then a student at the University of Glasgow. Robison prepared a rough sketch of his suggested steam-carriage, in which he proposed to place the cylinder with its open end downward, to avoid the necessity for using a working beam. Watt was then only twenty-three years old, and was very much occupied in conducting his business of a mathematical instrument maker, which he had only recently established. Nevertheless, he proceeded to construct a model locomotive provided with two cylinders of tin-plate, intending that the pistons and their connecting-rods should act alternately on two pinions attached to the axles of the carriage-wheels. But the model, when made, did not answer Watt's expectations; and when, shortly after, Robison left college to go to sea, he laid the project aside, and did not resume it for many years.
In the mean time, an ingenious French mechanic had taken up the subject, and proceeded to make a self-moving road engine worked by steam-power. It has been incidentally stated that a M. Pouillet was the first to make a locomotive machine,[13] but no particulars are given of the invention, which is more usually attributed to Nicholas Joseph Cugnot, a native of Void, in Lorraine, where he was born in 1729. Not much is known of Cugnot's early history beyond that he was an officer in the army, that he published several works on military science, and that on leaving the army he devoted himself to the invention of a steam-carriage to be run on common roads.
It appears from documents collected by M. Morin that Cugnot constructed his first carriage at the Arsenal in 1769, at the cost of the Comte de Saxe, by whom he was patronized and liberally helped. It ran on three wheels, and was put in motion by an engine composed of two single-acting cylinders, the pistons of which acted alternately on the single front wheel. While this machine was in course of construction, a Swiss officer, named Planta, brought forward a similar project; but, on perceiving that Cugnot's carriage was superior to his own, he proceeded no farther with it.
When Cugnot's carriage was ready, it was tried in the presence of the Duc de Choiseul, the Comte de Saxe, and other military officers. On being first set in motion, it ran against a stone wall which stood in its way, and threw it down. There was thus no doubt about its power, though there were many doubts about its manageableness. At length it was got out of the Arsenal and put upon the road, when it was found that, though only loaded with four persons, it could not travel faster than about two and a quarter miles an hour; and that, the size of the boiler not being sufficient, it would not continue at work for more than twelve or fifteen minutes, when it was necessary to wait until sufficient steam had been raised to enable it to proceed farther.
The experiment was looked upon with great interest, and admitted to be of a very remarkable character; and, considering that it was a first attempt, it was not by any means regarded as unsuccessful. As it was believed that such a machine, if properly proportioned, might be employed to drag cannon into the field independent of horse-power, the Minister of War authorized Cugnot to proceed with the construction of a new and improved machine, which was finished and ready for trial in the course of the following year. The new locomotive was composed of two parts, one being a carriage supported on two wheels, somewhat resembling a small brewer's cart, furnished with a seat for the driver, while the other contained the machinery, which was supported on a single driving-wheel 4 ft. 2 in. in diameter. The engine consisted of a round copper boiler with a furnace inside provided with two small chimneys, two single-acting 13-in. brass cylinders communicating with the boiler by a steam-pipe, and the arrangements for communicating the motion of the pistons to the driving-wheel, together with the steering-gear.
CUGNOT'S ENGINE.
The two parts of the machine were united by a movable pin and a toothed sector fixed on the framing of the front or machine part of the carriage. When one of the pistons descended, the piston-rod drew with it a crank, the catch of which caused the driving-wheel to make a quarter of a revolution by means of the ratchet-wheel fixed on the axle of the driving-wheel. At the same time, a chain fixed to the crank on the same side also descended and moved a lever, the opposite end of which was thereby raised, restoring the second piston to its original position at the top of the cylinder by the interposition of a second chain and crank. The piston-rod of the descending piston, by means of a catch, set other levers in motion, the chain fixed to them turning a half-way cock so as to open the second cylinder to the steam and the first to the atmosphere. The second piston, then descending in turn, caused the driving-wheel to make another quarter revolution, restoring the first piston to its original position; and the process being repeated, the machine was thereby kept in motion. To enable it to run backward, the catch of the crank was arranged in such a manner that it could be made to act either above or below, and thereby reverse the action of the machinery on the driving-wheel. It will thus be observed that Cugnot's locomotive presented a simple and ingenious form of a high-pressure engine; and, though of rude construction, it was a highly-creditable piece of work, considering the time of its appearance and the circumstances under which it was constructed.
Several successful trials were made with the new locomotive in the streets of Paris, which excited no small degree of interest. Unhappily, however, an accident which occurred to it in one of the trials had the effect of putting a stop to farther experiments. Turning the corner of a street near the Madeleine one day, when the machine was running at a speed of about three miles an hour, it became overbalanced, and fell over with a crash; after which, the running of the vehicle being considered dangerous, it was thenceforth locked up securely in the Arsenal to prevent its doing farther mischief.