SECTIONAL TRANSACTIONS.— G. 381 



high velocity. To prove this, experiments wore made upon metalHo conductors in 

 which there was a sudden change of section. By measurements taken on reversal of 

 the current a limiting value of electron velocity in metals was obtained and shown 

 to be far higher than that of the ions in a solution. This, in the author's opinion, 

 introduces phenomena at the cathode which hitherto have been neglected, but which 

 are plainly visible in the case of silver nitrate. This is sufficient to explain the 

 observed differences between the magnetic fields due to metallic and electrolytic 

 conduction. 



The conclusion is that the usual assumptions concerning the relationship between 

 current and electron or proton movement are correct for metallic and for electrolytic 

 conductors, but that, where a circuit contains both, the new electrode phenomena 

 must be taken into account. 



Monday, August 9. 



7. Mr. H. E. WiMPERis. — The Rotating Wing in Aircraft. 



The employment in aircraft of a rotating wing has long had a fascination for 

 inventors, but in spite of all their efforts very few machines fitted with rotating wings 

 for sustentation have flown as much as a kilometre. 



The requirement of safe descent with the power plant out of action is the most 

 important requirement for such machines, but to the designer it has proved hitherto 

 to be the most baffling. 



It had for long been thought it must be quite impossible for any rotating-wing 

 machine to rival the very slow speed of descent of a parachute having the same over- 

 all diameter and carrying the same load. But actually the Cierva gyroplane tested at 

 Farnborough in 1925 showed a degree of sustentation in vertical descent far in advance 

 of this standard. A parachute carrying the same load and of the same diameter as 

 the gyroplane would have descended twice as fast. 



The mode of flight of a practical flying-machine like the gyroplane affords the best 

 means of studying the performance of all types of rotating-wing machines. In this way 

 it is practicable to proceed from the known to the unknown, rather than by an 

 endeavour to proceed ab initio with an aircraft of entirely novel aerodynamic quality. 

 The next step towards the unknown is to study the effect of applying a power drive 

 to the windmill, at first when ' getting off,' and later when in flight. The issue may be 

 a successful helicopter, or it may not ; but in any case it is possible to cease exploration 

 at the form of machine which gives the best combination of advantages, and at the 

 worst there still remains a successful gyroplane. 



The author makes use of Major Low's diagram to show how the speed of rotation 

 of the wings is related to the load carried and to the landing speed. 



An interesting feature brought out in this manner is that the process of climb and 

 fall is continuous. There is no question of having to reverse the pitch of the blades or 

 the direction of rotation. A reversal of rotation of the windmill is for reasons of safety 

 obviously undesirable at any time; a change of pitch angle may on occasion, however, 

 prove very useful — as when" arising or alighting. But the construction shows that even 

 with a constant pitch angle and a constant direction of rotation, steady and safe 

 vertical motion is possible whether the windmill shaft is provided with a power drive 

 or not. 



The rotating-wing type of aircraft has certainly a future, but to what extent and 

 in what fields it will prove to possess an advantage over the fixed-wing type remains 

 yet to be determined. 



8. Mr. D. R. Pye. — High Duty Compression-Ignition Engines. 



Research was initiated in 1922 by the Air Ministry to explore the possibility of 

 developing a compression-ignition engine burning heavy oil of a weight/power ratio 

 possible for air work. In such an engine simplicity and lightness necessitate the direct 

 injection of fuel without air compressors. Although the weight/power ratio is still 

 prohibitive for air work, big advances have been made in regard to the output 

 obtainable from a given size of cylinder with this type of engine. The present-day 

 aircraft petrol engine weighs about 2 lb. per H.P. or less, and although the greater 

 fuel economy of the compression-ignition engine will compensate, to some extent,. 



