.s//? WILLIAM SIEMENS, F.R.S. 335 



cal line. In this respect I think Sir William demonstrates against 

 himself; but if we can lay down any certain rule this apparatus 

 is a great achievement. 



I have sent the wire sounding apparatus out with every ship I 

 have had lately to fit for sea ; and I am quite sure the meeting 

 will accord a hearty vote of thanks to Sir William Thomson for 

 his valuable communication. 



In the discussion of the Paper 



"ON COMPRESSED AIR-MACHINERY FOR UNDER- 

 GROUND HAULAGE," by MB. WILLIAM DANIEL, 



MR. C. W. SIEMENS * observed that in the preceding discussion 

 the question of the transmission of power by hydraulic pressure 

 had been considered, and certain losses attendant upon that plan 

 had been pointed out, while on the other side the great advantages 

 of hydraulic power in admitting of direct application to the work 

 had been duly appreciated. Another equally important question 

 was that now brought forward the transmission of power by an 

 elastic medium. The application of air power must necessarily be 

 quite different from that of water pressure, and might be resorted 

 to with great advantage in cases where steam could not be used 

 direct or where long steam-pipes would be objectionable ; and 

 among the numerous applications for which it was particularly 

 suitable, the most prominent and useful was that of underground 

 haulage, which formed the subject of the present paper. The 

 advantages of air power for this purpose were self-evident : in a 

 mine, surcharged as it was with heat, the use of steam would be 

 attended with great inconvenience ; whereas air, being rendered 

 by expansion so much colder than the prevailing temperature of 

 the mine, was the very medium required for such a situation. 



The subject therefore resolved itself into the question whether the 



* Excerpt Minutes of Proceedings of the Institution of Mechanical Engineer*, 

 1874, pp. 217-219. 



