AT an evening discourse delivered before members of the British Association on Sept. 29, Mr. H. E. Wimperis, Director of Scientific Research to the Air Ministry, gave an interesting résumé of accomplishments, and speculations as to future advances, in high speed flying. The very high accelerations set up have given rise to various problems, both structural in the aircraft and physiological in the occupant. A rate of three times tnat of gravity can be obtained in starting by the use of catapults. These are necessary for obtaining the minimum speed for flight for fast machines in a reasonable space. It is interesting to note that this rate of increase of speed is about a hundred times that of a steam-engined railway train. Even greater accelerations are experienced in curved flight—up to five times gravity—and as the machine is only designed to withstand a load of 8g, care has to be exercised, in making rapid turns of small radius, not to approach this. The centrifugal force on the pilot in such turns drives the blood from his brain to the more distensible parts of his body, and this is accompanied by a loss of sight, although not of mental clarity.