CHAP. V.] THE STEAM-BLAST. 171 in 1804, of Hedley in 1814, of Goldsworthy Gurney in 1820, and of Timothy Hackworth in 1829. With respect to Trevithick, it appears that he discharged the waste steam into the chimney of his engine, but without any intention of thereby producing a blast;* and that he attached no value to the expedient is sufficiently obvious from the fact that in 1815 he took out a patent for urging the fire by means of fanners, similar to a winnowing machine. The claim put forward on behalf of William Hedley, that he invented the blast-pipe for the Wylam engine, is sufficiently contradicted by the fact that the Wylam engine had no blast-pipe. "I remember the Wylam engine," Robert Stephenson wrote to the author in 1857," and I am positive there was no blast-pipe." On the contrary, the Wylam engine embodied a contrivance for the express purpose of preventing a blast. This is clearly shown by the drawing and description of it contained in the first edition of Nicholas Wood's "Practical Treatise on Railroads," published in 1825. This evidence is all the more valuable for our purpose as it was published long before any controversy had arisen as to the authorship of the invention, and, indeed, before it was believed that any merit whatever belonged to it. And it is the more remarkable, as Nicholas Wood himself, who published the first practical work on railways, did not at that time approve of the steam-blast, and referred to the Wylam engine in illustration of how it might be prevented. The following passage from Mr. Wood's book clearly describes the express object and purpose for which George Stephenson invented and applied the steam-blast in the Killingworth engines. Describing their action, Mr. Wood says: "The steam is admitted to the top and bottom of the piston by means of a sliding valve, which, being moved up and down alternately, opens a communication between the top and bottom of the cylinder and the pipe that is open into the chimney and turns up *It must, however, be mentioned that Mr. Zerah Colburn, in his excellent work on "Locomotive Engineering and the Mechanism of Railways," points out that Mr. Davies Gilbert noted the effect of the discharge of the waste steam up the chimney of Trevithick's engine in increasing the draught, and wrote a letter to "Nicholson's Journal" (Sept., 1805) on the subject; and Mr. Nicholson himself proceeded to investigate the subject, and in 1806 he took out a patent for "steam-blasting apparatus," applicable to fixed engines, which, however, does not seem to have come into use. (See ante, p. 82.) within it. The steam, after performing its office within the cylinder, is thus thrown into the chimney, and the power with which it issues will be proportionate to the degree of elasticity; and the exit being directed upward, accelerates the velocity of the current of heated air accordingly."* And again, at another part of the book, he says: "There is another great objection urged against locomotives, which is, the noise that the steam makes in escaping into the chimney; this objection is very singular, as it is not the result of any inherent form in the organization of such engines, but an accidental circumstance. When the engines were first made, the steam escaped into the atmosphere, and made comparatively little noise; it was found difficult then to produce steam in sufficient quantity to keep the engine constantly working, or rather to obtain an adequate rapidity of current in the chimney to give sufficient intensity to the fire. To effect a greater rapidity, or to increase the draught of the chimney, Mr. Stephenson thought that by causing the steam to escape into the chimney through a pipe with its end turned upward, the velocity of the current would be accelerated, and such was the effect; but, in remedying one evil, another has been produced, which, though objectionable in some places, was not considered as objectionable on a private railroad. The tube through the boiler having been increased, there is now no longer any occasion for the action of the steam to assist the motion of the heated air in the chimney. The steam thrown in this manner into the chimney acts as a trumpet, and certainly makes a very disagreeable noise. Nothing, however, is more easy to remedy, and the very act of remedying this defect will also be the means of economizing the fuel." Mr. Wood then proceeds to show how the noise caused by the blast-how, in fact, the blast itself, might be effectually prevented by adopting the expedient employed in the Wylam engine; which was, to send the exhaust steam, not into the chimney (where alone the blast could act with effect by stimulating the draught), but into a steam-reservoir provided for the purpose. His words are these: Nothing more is wanted to destroy the noise than to cause the * Nicholas Wood, "Practical Treatise on Railways," ed. 1825, p. 147. CHAP. V.] THE STEAM-BLAST. 173 steam to expand itself into a reservoir, and then allow it to escape gradually to the atmosphere through the chimney. Upon the Wylam railroad the noise was made the subject of complaint by a neighboring gentleman, and they adopted this mode, which had the effect above mentioned."* ment. It is curious to find that Mr. Nicholas Wood continued to object to the use of the steam-blast down even to the time when the Liverpool and Manchester Railway Bill was before ParliaIn his evidence before the Committee on that Bill in 1825, he said: "Those engines [at Killingworth] puff very much, and the object is to get an increased draught in the chimney. Now (by enlarging the flue-tube and giving it a double turn through the boiler) we have got a sufficiency of steam without it, and I have no doubt, by allowing the steam to exhaust itself in a reservoir, it would pass quietly into the chimney without that noise." In fact, Mr. Wood was still in favor of the arrangement adopted in the Wylam engine, by which the steam-blast had been got rid of altogether. If these statements, made in Mr. Wood's book, be correct-and they have never been disputed-they render it perfectly clear that George Stephenson invented and applied the steam-blast for the express purpose of quickening combustion in the furnace by increasing the draught in the chimney. Although urged by Wood to abandon the blast, Stephenson continued to hold by it as one of the vital powers of the locomotive engine. It is quite true that in the early engines, with only a double flue passing through the boiler, run as they were at low speeds, the blast was of comparatively less importance. It was only when the improved passenger engine, fitted with the multitubular boiler, was required to be run at high speeds that the full merits of the blast were brought out; and in detecting its essential uses in this respect, and sharpening *Nicholas Wood, "Practical Treatise on Railways," ed. 1825, p. 294. These passages will be found in the first edition of Mr. Wood's work, published in 1825. The subsequent editions do not contain them. A few years' experience wrought great changes of opinion on many points connected with the practical working of railways, and Mr. Wood altered his text accordingly. But it is most important for our present purpose to note that, in the year 1825, long before the Liverpool and Manchester line was opened, Mr. Wood should have so clearly described the steam-blast, which had been in regular use for more than ten years in all Stephenson's locomotives employed in the working of the Killingworth railway. it for the purpose of increasing its action, the sagacity of Timothy Hackworth, of Darlington, is entitled to due recognition. CHAP. VI.] ACCIDENTS IN MINES. 175 CHAPTER VI. 66 INVENTION OF THE GEORDY" SAFETY-LAMP. EXPLOSIONS of fire-damp were unusually frequent in the coalmines of Northumberland and Durham about the time when George Stephenson was engaged in the construction of his first locomotives. These explosions were often attended with fearful loss of life and dreadful suffering to the work-people. Killingworth Colliery was not free from such deplorable calamities; and during the time that Stephenson was employed as brakesman at the West Moor, several "blasts" took place in the pit, by which many workmen were scorched and killed, and the owners of the colliery sustained heavy losses. One of the most serious of these accidents occurred in 1806, not long after he had been appointed brakesman, by which ten persons were killed. Stephenson, was near the pit mouth at the time, and the circumstances connected with the explosion made a deep impression on his mind, as appears from the graphic account which he gave of it to the Committee of the House of Commons on accidents in mines, some thirty years after the event. "The pit," said he, "had just ceased drawing coals, and nearly all the men had got out. It was some time in the afternoon, a little after midday. There were five men that went down the pit; four of them for the purpose of preparing a place for the furnace. The fifth was a person who went down to set them to work. I sent this man down myself, and he had just got to the bottom of the shaft about two or three minutes when the explosion took place. I had left the mouth of the pit, and had gone about fifty or sixty yards away, when I heard a tremendous noise, looked round, and saw the discharge come out of the pit like the discharge of a cannon. It continued to blow, I think, for a quarter of an hour, discharging every thing that had come into the current. Wood came up, stones came up, and trusses of hay that went up into the air like balloons. Those trusses had been sent down during the day, and I think they had in some measure injured the ventilation of the |