526 SCIENCE PROGRESS 



Slate, F., An Alternative View of Relativity, Phil. Mag. (vi), 39, 1920, 

 433-9 ; the author's view is that relativists need not reject Newtonian 

 dynamics, which can be so extended as not to contradict relativity. 



Majorana, L., Experiences sur la gravitation, Comptes Rendus, 169, 1919, 

 7 1 9-2 1, discussing the absorption of gravitation in passing through masses. 



Forsyth, A. R., Note on the Central Differential Equation in the Relativity 

 Theory of Gravitation, Proc. Roy. Soc, 97, 1920, 145-51, where it is 

 shown that the motion of a planet round the sun according to Einstein's 

 theory can be solved in terms of elliptic functions. 



The impetus given to hydro- and aero-dynamical research 

 by the development of the science and art of aeronautics is 

 producing work of importance both to the applied mathe- 

 matician and to the aeronautical and marine engineer. A 

 recent and important contribution to the study of fluid resistance 

 and of motion in resisting media is the Bulletin de V Institut Aero- 

 dynamique, fasc. vi, 1920, containing a number of papers by 

 D. P. Riabouchinski, working at Koutchino, By the use of a 

 function defined in a discontinuous manner, the author discusses 

 problems on the discontinuous motion of fluids with various 

 types of barriers. He also investigates the resistance of air at 

 high velocities, and further work includes the autorotation of 

 a projectile in air (due to suction caused by the formation of 

 vortices behind the projectile), the efflux of gas from a receptacle, 

 and air-screws. 



Of equal importance, from another point of view, is 

 The General Theory of Blade-screws {First Memoir) ^ by George 

 de Bothezat, published as Report No. 29 by the National Ad- 

 visory Committee for Aeronautics, Washington, U.S. A., 19 19. 

 Bothezat has long been engaged in this work (see Science 

 Progress, xiii, 191 8, 187) ; he worked in Russia till the 

 revolution, and has continued his work in America. While 

 one finds it difficult to assent to the author's opinion that the 

 theory of blade-screws is an important state question for every 

 Government, and that special laboratories should be established 

 to study screws in the light of his theory, one cannot doubt 

 the importance of the subject and of his theory. The theory 

 is ambitious and includes " Propellers, Fans, Helicopter Screws, 

 Helicoidal Pumps, Turbo Motors, and different kinds of 

 Helicoidal Brakes." After giving the fundamental equations 

 relating to blade-screws based on what Bothezat calls the 

 specific function, which is a function of the relative pitch, the 

 author proceeds to distinguish sixteen states of work of blade- 

 screws, including the vortex ring state and whirling phenomena. 

 The most important section of the report deals with the pro- 

 pulsive screw or propeller, and nomograms are given for finding 

 solutions on the author's theory. A note of considerable interest 

 gives a generalisation of Bernoulli's theorem to include vortex 

 motion. 



