"A. Where the draught has been sluggish; I used it to get a stronger draught on board a steamboat in 1830, to enable me to stem the strong currents of the Garonne.
"Q. Have you any knowledge of some experiments made by Mr. Gurney in the year 1826 with respect to the power of the steam-jet?
"A. I saw frequent experiments made by Mr. Gurney in 1826 to produce draught by the action of high-pressure steam, exactly in the same way as it is now employed for producing ventilation in the collieries; that is, there were a number of jets of about a quarter to three-eighths of an inch diameter, communicating directly with a high-pressure boiler; the cock being open, the full steam from the boiler was brought upon those jets, and a draught was produced by their action in the chimney-shaft.
"Q. In the chimney-shaft of a locomotive engine?
"A. In the chimney-shaft of a locomotive and in the shaft of a factory; the experiments were tried in various ways. I saw these experiments frequently; many other persons saw them at the same time; and I employed the same myself shortly afterwards for a like purpose abroad."
Mr. Keene in his evidence further stated, in answer to the question whether Mr. Gurney's experiments were open to the public:—
"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.