had become successfully established by others, who reaped the fruits of his unrecompensed exertions.

The earlier boilers employed by Trevithick usually consisted of cylinders of cast iron. The fire-place was situated in a wrought iron tube passing through the boiler from one end to the other. The internal tube in some cases was made to return again through the boiler, the chimney being placed at the same end of the boiler as the fire door. Subsequently he adopted cylindrical boilers made of wrought iron plates.

The pressure of steam used by Trevithick was very variable, sometimes as low as twenty pounds on the square inch, but on one occasion we find him pressing a boiler as high as 145 pounds. The danger of using highly elastic steam was not found to be so great as had been apprehended by Watt. On the occasion of the bursting of a boiler at Greenwich, in 1803, by which three persons were killed on the spot, and a fourth fatally injured, Boulton and Watt endeavoured to procure an Act of Parliament to put a stop to the use of high-pressure steam as dangerous to the public. Their efforts only led to an inquiry being made by Government engineers, as to the strength of the materials used in the construction of the highpressure engines. The accident in 1803 was clearly traceable to neglect. The boy who had charge of the engine had gone to catch eels in the foundation of the building, leaving the care of it to a labourer. This

XVII.] WATT DENOUNCES TREVITHICK'S ENGINE. 211

man, seeing the engine going much faster than usual, stopped it, without taking off a spanner which fastened down the steam-lever. The explosion followed a short time afterwards. The boiler in this case was of a globular form; it was six feet in diameter, and made of cast iron about one inch thick. It burst in all directions. One piece, weighing about five cwts., was thrown upwards of 125 yards. In consequence of this accident Trevithick determined to employ two steamvalves, and a steam-gauge, in future, and never again to let the fire come in contact with cast iron. The boiler had been heated red hot, and all the joints burnt, a few days before the explosion.1

2

Watt is stated to have declared that Trevithick "deserved hanging" for introducing the high-pressure steam engine; but the force of public opinion went against him. The value of the machine was considered to more than outweigh any risk attached to its use.

1 Life of Trevithick, by F. Trevithick, Vol. II., p. 124-6, and Vol. I., p. 162.

2 Ibid., Vol. II., p. 395.

CHAPTER XVIII.

RENEWED ATTEMPTS TO EMPLOY LOCOMOTIVE ENGINES

.

ON RAILWAYS.-ITS SUCCESSFUL ACCOMPLISHMENT.

THOUGH Mr. Blackett, of Wylam, had for some reason declined to take the locomotive engine made for him in 1805, he appears never to have abandoned the idea of ultimately adopting this means of haulage. in lieu of horses on his waggonway. It was doubtless with this end in view that he reconstructed his railway about the year 1808, taking up the wooden rails previously employed, and replacing them by cast iron plate-rails, as we find him writing to Trevithick in 1809 on the subject of an engine. In his reply, Trevithick stated that he was engaged in other pursuits, and having declined the business, he could render no assistance.1

No further steps were taken by Mr. Blackett at the time, but the attention of others had also been directed

1 Who Invented the Locomotive? by O. D. Hedley, published 1858; Life of Trevithick, by F. Trevithick, Vol. I., p. 196.

CH. XVIII.] BLENKINSOP PATENTS THE RACK-RAIL. 213

1

to the subject of steam locomotion. On the 10th of April, 1811, a patent 1 was granted to "John Blenkinsop, of Middleton, in the parish of Rothwell, in the county of York, coal viewer, for his invented certain mechanical means by which the conveyance of coals, minerals, and other articles, is facilitated, and the expense is rendered less than heretofore." The special object which Blenkinsop had in view was the conveyance of coals on the railway from Middleton Collieries to Leeds, a distance of about three and a half miles. The special feature of his invention consisted in the use of a rackrail fixed in the centre of the railway, or forming part of the rails on one side. No form of locomotive engine is included in Blenkinsop's patent (Trevithick and Vivian's patent for the application of the high-pressure engine to propelling carriages being still in force), but the "steam engine" is mentioned as the motive power most suitable for the purpose. Blenkinsop employed the then celebrated firm of engineers, Messrs. Fenton, Murray, and Wood, of Leeds, to construct locomotive engines for him. At the suggestion of Mr. Murray, the leading spirit of the firm in engineering matters, each locomotive was provided with two double-acting cylinders,2 now first employed in the locomotive engine.

1 No. 3431.

2 Locomotive Engineering, &c., by Zerah Colburn, 1871, p. 15; Smiles's Lives of the Engineers-" George and Robert Stephenson," ed. 1874, p. 72.

This was a great improvement, a regular and steady action being obtainable from it without the use of a flywheel. The engine (Fig. 44) was mounted on a frame of timber with smooth wheels, and drove a pinion working in the rack-rail, thus propelling itself and the load

attached to it. The application of the rack enabled a comparatively light engine to haul a heavy train of waggons, and to ascend gradients which the smoothwheeled locomotive used by Trevithick could not have surmounted.