a. Ball and socket jet at an angle, and discharging steam. The egg-shells are supported by the enormous current of air moving into the jet in the direction of the arrows.
In consequence of the great rush of air towards a jet of escaping high-pressure steam, Mr. Goldsmith Gurney has patented the application of this principle in his ventilating steam jet, which he has already successfully applied; in one case especially, where a coal-mine had been on fire for several years, and the whole working of the coal-measures in the pit was jeopardized by the spreading of the combustion to new workings; the fire was first extinguished by carbonic acid gas, pulled, as it were, into the coal-mine by a jet of steam blowing into the downcast, but placed in connexion with a furnace of burning coke; and the circulation of the carbonic acid, called choke-damp, through the pit workings was further assisted by a jet of high-pressure steam blowing upwards, and placed over the mouth of the upcast shaft.
The experiment succeeded perfectly at the South Sauchie Colliery, near Alloa, about seven miles from Stirling, where a fire had raged for about thirty years over an area of twenty-six acres in the waste seam of coal nine feet thick. (Fig. 386.)
Fig. 386.
Gurney's steam jet. a. Furnace. b. Water tank. c. Downcast stopping. d. Upcast stopping. e e e. Steam jets. f f. Galleries from shaft to shaft.
For the general purpose of ventilating the coalmine, Mr. Gurney's plan was tried at the Ebbw Vale Colliery, and very economically, the waste steam alone being used. Experiments have also been satisfactorily made with it for blowing a cupola for smelting iron, and with dry steam—i.e., steam of a very high pressure—escaping through a warm tube, the results were perfectly successful.
With this digression from the subject of latent heat derived from the compression of air, we return again to the subject with another case in point, furnished by the Fountain of Hiero, as it is called, at Schemnitz, in Hungary, described by Professor Brande; and it may be observed that all the phenomena related would apply to the great pressure of the water from the water-towers at the Crystal Palace, if fitted with a similar air-vessel.
"A part of the machinery for working these mines is a perpendicular column of water 260 feet high (the Crystal Palace water-towers are each 284 feet high), which presses upon a quantity of air enclosed in a tight reservoir; the air is consequently condensed to an enormous degree by this height of water, which is equal to between eight and nine atmospheres; and when a pipe communicating with this reservoir of condensed air is suddenly opened, it rushes out with extreme velocity, instantly expands, and in so doing it absorbs so much heat as to precipitate the moisture it contains in a shower of snow, which may readily be gathered on a hat held in the blast. The force of this is so great, that the workman who holds the hat is obliged to lean his back against the wall to retain it in its position."