526 SCIENCE PROGRESS 



pay any attention to the study of aeronautics, and the most 

 mystifying phenomenon in this connection is the problem of 

 soaring flight. Many explanations have been attempted of a 

 matterwhich seems to defy the principles of mechanics. Recently 

 a further attempt at an explanation was made by R. de Villa- 

 mil in a pamphlet published in London in 1920 (Spon). His 

 explanation, however, is not satisfactory, and the mystery 

 remains unsolved. E. H. Hankin has been studying bird-flight 

 for a considerable number of years, and he discusses the problem 

 of soaring flight in two papers, Proc. Camb. P.S., xx, 192 1, 219- 

 27, 460-5. He comes to the conclusion that this form of flight 

 is not due to undiscovered wing movements, to lateral gusts of 

 wind, to ascending gusts, or to convection currents produced 

 by the sun's heat. He thinks that the problem is at present 

 inexplicable, and suggests experimental investigation of the 

 phenomenon. Soaring flight is known in connection with such 

 differently constituted bodies as birds, flying-fishes, and 

 dragon-flies, and Hankin thinks that low speeds are to be 

 attributed to sunshine, while high speeds are to be attributed 

 to wind. 



A mild sensation has been caused by G, Brewer's " The 

 Langley Machine and the Hammondsport Trials," Aer. Jour., 

 xxv, 1 92 1, 620-64, wherein the author contends that the credit 

 for having been the first to fly in an aeroplane is due entirely to 

 the Wright brothers, and contests the claim that has been 

 raised on behalf of Langley. Brewer brings evidence to show 

 that the successful flights of the Langley machine carried out in 

 19 14 were due to the very considerable modifications made in 

 the original machine of 1903. There are replies by supporters 

 of the Langley claim to priority. 



Of great interest to the applied mathematician is the dyna- 

 mical problem of the actual behaviour of an aeroplane in the 

 air, including such questions as the greatest and least possible 

 velocities of horizontal flight, the angle of glide for various 

 configurations of the elevator, the rate of climb at different 

 levels, the height the aeroplane can reach, or " ceiling," etc. To 

 the student of dynamics the subject affords an excellent oppor- 

 tunity of useful research, of all grades of difficulty. The general 

 problem is of great complexity, but the simpler questions that 

 the practical designer is content to ask can be answered at the 

 expense of quite elementary mathematics. A very useful 

 and easy account of such mathematical processes has been 

 written by H. Booth, entitled, " Aeroplane Performance Cal- 

 culations " (Pp. xvi-f 207, Chapman & Hah, London, 1921, 

 2 IS. net.). Mr. Booth's main object is to supply the designer 

 with methods of calculating beforehand what the machine he is 

 designing will do when it is taken up into the air, and in carrying 



