342 



SCIENCE. 



[N. S. Vol. XVI. No. 400. 



proposed to stimulate it. They have de- 

 cided to offer liberal prizes and to enforce 

 conditions which will call out the best 

 efforts of the best investigators. 



They specify no device or machine ; they 

 base everything on performance, on a re- 

 turn course requiring a high degree of con- 

 trol. They have fixed a minimum which 

 greatly exceeds any recorded mas.imum. 



Before reading their rules the author 

 wishes to call attention to two consider- 

 ations touching the possibility of progress 

 and the probable line of approach. 



Rapid progress is being made in the 

 matter of reducing the weight of prime 

 movers per horse-power. The diminution 

 of the steam-boiler, as shown by the gas- 

 engine and the Diesel motor, has made it 

 quite possible to construct an engine as 

 strong as a horse and as heavy as a goose. 

 Human ingenuity will surely suffice some- 

 time to enable such an engine to fly. 



The skillful teacher at the swimming 

 school gently buoys up the novice while he 

 learns how to move his arms and legs. As 

 his pupil masters the movements and co- 

 ordinates the strokes he needs less and less 

 of help from the fish-pole and line of the 

 instructor, and soon he swims without 

 assistance and to his great surprise. 



Will it not be so with the navigator of the 

 air? At first he needs the buoyancy of a 

 balloon attachment while he elaborates his 

 propellers, planes and guides. As these 

 increase in efficiency the balloon attachment 

 diminishes, until finally it may disappear 

 altogether. Who can say it will not? The 

 writer has no hope from the balloon pure 

 and simple. He has at present small hope 

 of a pure flying machine ; but he has great 

 hope of a device which, while flying, 

 accepts more or less aid from a buoyant 

 gas. 



New Methods of Experimentation in Aero- 

 dynamics: A. F. Zahn. 



In this paper Zahn outlines some re- 

 searches in aerodynamics by Mr. MattuUath 

 and himself at the Catholic University of 

 America. Their investigations cover a 

 variety of subjects important to the science 

 of practical dynamic flight, but the paper 

 is confined mainly to the description of a 

 new laboratory and equipment for genera- 

 ting a uniform rectilinear flow of air and 

 measuring its effects upon various models 

 and shapes of scientific and practical in- 

 terest—in other words, the description of 

 an aerial ' model basin. ' 



In a special building erected on the 

 campus by Mr. ]\Iattullath is a wooden air 

 tunnel fifty feet long by six feet square in 

 cross sections, having a five-foot suction fan 

 at one end and a netting or two of close mesh 

 at the other. A wind is thereby generated 

 of practically uniform velocity and direc- 

 tion, the speed vai'ying less than one per 

 cent., the direction but a small fraction of 

 a degree. In this current are held objects 

 whose lift, drift, skin-friction, etc., are to 

 be measured. 



A general description is given of the 

 apparatus for generating and controlling 

 the wind, the devices for proving its uni- 

 formity of velocity and direction, the in- 

 struments for measiiring its effects on 

 immersed bodies. Among the various ane- 

 mometers and wind balances designed is a 

 pressure gauge graduated to millionths of 

 an atmosphere, and which may be adjusted 

 to read to less than one ten-miUionth. It 

 is connected by hose to one or more Pitot 

 nozzles, and is used to measure the air 

 velocity and pressure at all points of the 

 stream, particularly in the neighborhood of 

 the exposed body. 



The results of each investigation will be 

 given in technical detail in a series of 

 papers, excepting those that are withheld 

 for business reasons. The prime motive of 

 these researches is to furnish a basis for 



