TRANSACTIONS OF SECTION G. 483 



Conclusions. — Apart from the question of stability, progress in flying-machine 

 design is mainly a problem of increasing the efficiency of the machine, just as it 

 is in every other branch of mechanical engineering. It follows, therefore, that 

 the need for further information on such subjects as the effective angle of a 

 plane, sweep, skin friction, and other similar problems that come within the 

 province of research work in physical science, is all important. If the aeroplane 

 of the future is to carry heavy loads and to fly far and fast without interrupting 

 its journey, it must be more efficient than the aeroplane of to-day. The air, like 

 the ocean, permits of full speed ahead all the time, and a speed of 60 miles 

 per hour through the air would halve the present fastest crossing of the Atlantic. 

 Before an uninterrupted journey across the 1,700 miles that separate the nearest 

 adjacent points of land could be accomplished by a machine carrying only two 

 men it would have to be shown that an aeroplane could be built capable of carry- 

 ing at least 1,500 lb. of useful load at 60 miles per hour, with a gliding angle 

 more nearly in the order of 1 in 7 than the angle of 1 in 4 or 5 which at 

 present represents the efficiency of a good modern flyer. 



Except so far as a pilot might be able to economise power, as soaring birds do, 

 by taking advantage of favourable air-currents, skilful control has nothing to do 

 with the theoretical possibilities of the aeroplane in undertakings of this order, 

 which may be investigated by the aid of simple arithmetic. In matters affecting 

 the use of machines in bad weather, for dangerous purposes, and under difficulties 

 generally, nothing in the world gives any clue to the future except the present 

 state of the art, for which the intrepid practice of pilots and the care of thosa 

 who build machines is wholly responsible and deserving of the utmost credit. 



Summary of Formulae. 

 The two-thirds fewer law. — If thrust cc V 2 and power cc V 3 , then thrust oc 



H.P.*. 



Mathematics of the cambered plane. — 



V 2 tan 3 



Lift= — - 



200 



where V= flight speed m.p.h. 

 3 — angle of deflection. 

 Skin friction. — Zahm's formula — ■ 



R=0-000O316?-93V 186 

 Where R= resistance of double surface lb./ft. of span, 

 I = chord, 

 V = velocity m.p.h. 

 Approximation (1 to 90 m.p.h. and high aspect ratio) 

 R=0-000018V 2 . 



Coefficient of flight. — r (,,.«ii n-0072 



voemcient of jtignt. — r f,,, ?->_!. n-0072 ~| 



Pounds thrust per lb. loading = I — ,. . „ — 



Minimum value obtains when /? = 5° approx., and gives least coefficient of 

 flight =0-085. 



The following Papers were then read :— 



1. Recent Developments in Radio-Telegraphy. 

 By Professor G. W. O. Howe. 



The principal cause of the difficulties experienced to-day in maintaining 

 satisfactory communication by means of radio-telegraphy is to be found in the 

 phenomenal growth of this means of transmitting intelligence. The difficulties 

 are mainly due to interference between different stations working simultaneously. 

 Formerly the only disturbance was that due to atmospheric influences, but these 

 are now becoming of less comparative importance, due to the great multiplication 

 of radio-telegraphic equipments and the increasing power used in their sending 

 apparatus. These difficulties promise to increase steadily in the future, and it is 

 therefore a matter of some importance that we should consider the recent develop- 

 ments in the apparatus employed and in the principles involved. 



Nearly all the developments, both in the sending and in the receiving 



i i 2 



