"Many persons visited the place daily, and the carriage went out into the road, and into the barracks, and was often surrounded by a group of persons. It was understood and known how this draught was procured, because the passage of the steam was heard up the chimney when the carriage was still, and the great draught of the furnace was the occasion of remark by everybody who was around it; they were quite surprised how such a great current could be produced with so small a height of chimney: it was a very remarkable thing, and drew attention from everybody around at that time." The principle of the action of the steam-blast was simple enough. It was to fill the funnel with high-pressure steam, which would act much as the sucker in a pump, exhaust the air and draw up air through the furnace, as the cone of steam escaped out of the funnel. To act thus, the steam must completely fill the chimney, allowing of no down draught. This was what had entirely escaped Trevithick and Stephenson. Up to the discovery of the steam-jet by Gurney, the waste steam, as has been stated, was uselessly dispersed through the chimney. In 1827, Gurney took a steam-carriage he had constructed to Cyfarthfa, at the request of Mr. Crawshay, and while there applied his steam-jet to the blast-furnaces. This gave a great impetus to the manufacture of iron. Stephenson now adopted it, and employed it for his locomotive the _Rocket_, that ran on the Liverpool and Manchester Railway in October, 1829. Previously on one occasion Stephenson had run his engine continuously for fifty-three minutes doing twelve miles. But now, with the adoption of the steam-blast, it attained a velocity of twenty-nine miles an hour. "It is not too much to say that the success of the locomotive depended upon the adoption of the steam-blast. Without that, by which the intensity of combustion, and the consequent evolution of steam, were maintained at the highest point, high rates of speed could not have been kept up, the advantages of the multitubular boiler afterwards invented could never have been fairly tested, and locomotives might still have been dragging themselves unwieldily along at little more than five or six miles an hour."[13] It had been in July of the same year that Gurney had made a journey in his steam-coach from London to Bath and back again, on the main road, at the rate of fifteen miles an hour. This journey, undertaken at the request of the quartermaster-general of the army, was the first long journey at a maintained speed ever made by any locomotive on road or rail. Mr. Gurney's steam-coach was, of course, provided with the steam-jet.