SECTIONAL TRANSACTIONS.— G. 585 



of diecontinuity. Further it is shown that the vapour is always dry and saturated 

 at the nozzle throat. 



It is also shown that the acoustic velocity through the vapour changes suddenly 

 at the section of the nozzle where the vapour st^te changes. This discontinuity 

 confirms the statement that within the unique range of initial superheats specified, 

 the vapour at the throat is always in the dry and saturated state. 



Afternoon. 



Visit to Shipbuilding and Engineering Works of Messrs. John Brown, 

 Clydebank. 



Monday, September 10. 



Mr. A. E. L. Chorlton. — Oil Engines for Aircraft and Railways. 



Wing-Commander Cave-Brown-Cave. — Evaporative Cooling of Aero 



Engines. 



Prof. W. J. GouDiE. — Cycles for Internal Combustion Engines. 



Prof. E. F. D. WiTCHELL. — A Chart for the Determination of Internal 

 Combustion Engine Efficiencies. 



The paper discusses the modification in expressions for the ideal efiBciencies of 

 internal combustion engine cycles rendered necessary by the fact that the specific 

 heats of the working agent vary with temperature. 



The ideal efificiency depends on volume ratios, heat input and the temperature 

 at which compression begins, and a chart is described by the aid of which the ideal 

 efficiency of a cycle with given data may be easily determined. 



The expressions for the specific heats used for the construction of the chart are 

 those for permanent gases selected by the Institution of Civil Engineers in the recent 

 report on heat engine trials. 



Afternoon. 

 Visit to works of Messrs. D. Colville & Co., Clydebridge. 



Tuesday, September 11. 



Prof. W. Cramp. — The Possible Application of High Frequency Power to 

 Electric Traction. 



The idea of conveying electric power to a moving vehicle by induction (instead of 

 by conduction) is attractive, since sliding contacts are thereby avoided. Ayrton, 

 Perry and Mather appear to have made an attempt in 1S96 to develop a system on 

 this principle, but as they used ordinary power frequencies the wattless component 

 of current became unmanageable. In 1922 M. Maurice Leblanc proposed to use a 

 frequency of 20,000 p.p.s., and worked out (on paper) a complete system, using an 

 ionic h.f. generator of his own design for the primary supply. In his secondary 

 circuit on the train another ionic converter changed the single-phase current into 

 three-phase low-frequency current, which fed the motors. This arrangement involved 

 not only a tuned primary and secondary, but also a very special form of overhead 

 conductor, and complicated gear for maintaining the tuning with change of load. 

 The space occupied by the apparatus on the vehicle was very large, and M. Leblanc 

 does not seem to have published tests of his generator, nor to have constructed his 

 automatic tuning gear. 



In 1924 the author saw that automatic tuning is really a natural feature of the 

 Poulsen arc, and in consequence a generator of this type would immensely simplify 



