126 Sir Frederick Bramwell [May 19, 



ventilation, and the problem of how to ventilate under such circum- 

 stances, must be matters of difficulty. Everything points therefore 

 to the employment of machinery ; this must however be worked at 

 a distance from the original source of power. I say so because no 

 one would suggest that a steam engine, with its boiler and furnace, 

 should be used in such a position underground, and therefore we 

 must take it that the source of power will be situated on the shore. 

 Now in what manner is the power to be transported ? Fifty 

 years ago power was transported to such places by a mode still 

 perfectly practicable and feasible, namely, the making of a partial 

 exhaustion at the source of power by means of air-pumps, exhaust 

 mains connecting these pumps to the engine to be worked at a 

 distance. With this arrangement it will be seen that the pressure 

 of the atmosjihere exerted on the pistons of the engines, to the ex- 

 haust iuj)es of which the exhaust mains were connected, produced the 

 requisite power. 



This then was the system of conveyance of power by exhaustion, 

 and it had the merit of ventilating the place where it was being 

 worked, not, it is true, by air delivered at tlie working face, but by 

 air drawn in, if I may so phrase it, from the shaft, and all the way 

 along the heading to the working face to feed the engines which 

 were worked by the exhaustion. 



Another mode of conveying power in these days is by the laying 

 on of gas to work a gas motor. It is perfectly feasible, but the 

 result of using this mode would be, that the products of combustion 

 would vitiate the atmosphere nearly as badly as it would be vitiated 

 by the employment of coal-fires underground. This mode therefore 

 is unsatisfactory. 



Another mode would be by the conveyance of water under pressure ; 

 this has for many years been employed by Sir William Armstrong, 

 and others following him, to transmit power to a distance. Such a 

 system is free from the disadvantage of vitiating the air in any way, 

 but on the other hand it does not contribute to the ventilation. It 

 has, however, when coupled with the improvements made by Mr. 

 Crampton for the special purpose of tunnelling, advantages which 

 I shall describe later on. 



The most modern plan of conveying power, is its transmission by 

 electricity ; this, like the hydraulic mode, neither detracts from the 

 purity of the air, nor does it add to it. 



There remains, however, the converse of the exhaustion system, 

 which is the one commending itself, I think, upon many grounds as 

 being very applicable to the transmission of power to the end of a 

 long tunnel or heading. I mean the mode of working by com- 

 pressed air. 



This is extremely simple in its operation. Driven by a steam 

 engine on the surface there are compressing pumps which draw in 

 the atmospheric air, compress it to the desired degree, and this com- 

 pressed air is, by means of pipes, carried down the shaft and along 



