L. MECHANICS AND ENGINEERING. 447 



metal is still worth a large part of tlie original cost. 5 (7, 

 XLVIIL, 385. ' 



PEAT AS LOCOMOTIVE FUEL. 



Any method of treating peat, to enable it to be utilized on 

 a large scale, would be of great importance ; in which con- 

 nection it is of interest to notice that the Central Pacific 

 Railroad Company have experimented successfully with this 

 substance as fuel for their locomotives. Their supply was 

 obtained from an island at the junction of the Sacramento 

 and San Joachin Rivers in California. 4 j9, October 7, 1875, 

 15. 



THE PNEUMATIC TUBE IN THEORY AND PRACTICE. 



Mr. CuUey communicates to the Institute of Civil Engi- 

 neers, of London, an elaborate memoir on the transmission of 

 telegrams by pneumatic tubes. This, he says, was first car- 

 ried out in 1853 by Mr. Latimer Clark for the Electric and 

 International Telegraph Company in London. Both the 

 compressed air and the vacuum methods have been used in 

 England; and tubes having diameters of from one to three 

 inches are adopted according to the necessities of trafliic. 

 The methods adopted in London appear to secure decidedly 

 greater speed and certainty than those used in Paris. The 

 British public, it is stated, is perhaps exacting in its demands 

 for speed. A delay of ten minutes would be considered fatal 

 in the metropolitan traffic. As regards the comparative cost 

 of the pneumatic and the electric systems, it is stated that 

 the former is decidedly less expensive, since, for instance, the 

 total annual expense of the tube system in London, including 

 the pay of all engaged in it, and the interest on the original 

 cost, is barely two thirds of the pay alone of the staff that 

 would be required to telegraph the messages. The theoret- 

 ical principles which govern the flow of air through pipes, 

 and the amount of engine-power required to produce that 

 flow, has been very thoroughly investigated by the telegraph 

 officials of England, and the results of their investigations are 

 given \)Y Messrs. Culley and Sabine in the present memoir. 

 A number of experimental determinations were made by 

 using the tubes when business was not pressing, and the re- 

 sults thus obtained appear to verify the theoretical formula. 



