NATURE 



[February 27, 1913 



is unrortiinate that the growths produced experi- 

 mentally by Fibigcr present just as much difficulty 

 in the elucidation of the exact process as do all 

 other natural growths. 



In the past the attempt has often been made to 

 produce cancer by subjecting animals to the irrita- 

 lions associated with cancer in man, but without 

 success except possibly in the case of X-rays. As 

 the writer has pointed out, the irritants vary from 

 one mammal to another, and the knowledge of 

 ihe irritants to which different species and even 

 I heir individual organs are liai)le is of very con- 

 siderable importance, and will require extensive 

 study. Frof. I'"ibiger is to be congratulated not 

 only in having isolated such an apparent specific 

 irritant, but also, by carefully imitating the natural 

 process, on having produced cancer experimentally 

 through the mediate intervention of a parasite 

 liir Ihe first lime. K. F. IJasiikord. 



niE INTERNATIONAL AERO EMIlBrflON 

 AT OLYMPIA. 



rHV. development of the details of Hying 

 machines between igo8 and the present 

 lime is immediately obvious on a visit to the Aero 

 fvxhibition ; but, quite apart from the higher 

 standard of workmanship, it is also evident that 

 scientific principles are governing the design of 

 aeroplanes to a greater and greater extent. 

 .Vlmost without exception the designs show evi- 

 dence of the general desire to keep the resistance 

 of the machines as low as possible and so get 

 increased lifting power and speed. It is not any 

 longer necessary lo consider the bare possibility 

 of lift, as the shape of the wings is now so good 

 as to give about 30 lb. of lift per horse-power, 

 • ind engines available for aeroplanes can be 

 obtained of horse-powers up to 160, weighing less 

 I ban 3 lb. per horse-power; such an engine can 

 then carry, roughly, ri tons, a weight greater 

 than that of any existing aeroplane. 



The reduction of resistance does not then arise 

 from necessity, but appears to be directly due to 

 the application of scientific principles. The chief 

 saving in resistance arises from fewer slay-wires 

 and in the covering of the fuselage or tail girder 

 of almost all Hying machines, although there are 

 notable exceptions, such as the Maurice Farman 

 l)i[)laiie exhibited. As compared with the first 

 Wright machine, the stay-wiring of modern 

 machines looks comparatively simple, .md in 

 biplanes in particular the struts have been 

 lengthened in the direction of the wind. The 

 strength of the struts is often obtained from a 

 circular steel tube, the desired section for low 

 resistance being obtained from it by the addition 

 of wooden tails and headpieces. The difference of 

 resistance due to shaping the tubes may, on a 

 bil^lane, increase the carrying capacity of the 

 machine to the extent of another passenger. 



The covering of the fuselage to make a stream- 

 line body has, however, other effects than that of 

 reducing the resistance. The side surface is con- 

 siderable, and becomes equivalent to a vertical 

 fin; Prof. Bryan in his book on stability has 

 shown mathematically, what Mr. Lanchester 

 NO. 2 261, VOL. 90] 



deduced earlier from a combination of experiment 

 and mathematical analysis, that the position of 

 such fins is of the greatest importance when con- 

 sidering the lateral stability of an aeroplane, and 

 that great care must be taken in the arrange- 

 ment of such surfaces. 



One then looks at the exhibits to find how far 

 aeroplane constructors are designing according to 

 the principles of inherent stability, and how far 

 they leave the control to the skill of the pilot. 

 So far as longitudinal stability is concerned, prac- 

 tically all the machines at the normal flying speed 

 satisfy the mathematical requirements for the 

 stability of small oscillations. The essential 

 features of inherent stability are contained in a 

 series of planes inclined fore and aft, with the 

 angle of incidence from plane to plane decreasing 

 progressively from front to back and in addition 

 having the smaller or elevator planes of sufficient 

 area. Most of the machines, such as the Bl^riot, 

 BF 2, \c., have two surfaces, the main wings and 

 a neutral or nearly neutral tail, whilst the Cody 

 prize machine and the Maurice P'arman biplane 

 have each three planes due to the addition of a 

 forward elevator. 



Part of the tail plane, and usually the greater 

 part, is fixed to the fuselage of the flying machine, 

 and exercises a control which is independent of the 

 pilot, who is left with the adjustment of the 

 remainder for manceuvring. An exception to this 

 subdivision of the elevator occurs in the Breguet 

 machine, where the whole surface is under the 

 immediate control of the pilot. This latter ar- 

 rangement has the advantage of a powerful con- 

 trol and the corresponding possible disadvantage 

 of depending entirely on the strength of the pilot 

 for the maintenance of altitude. How much the 

 advantage outweighs the disadvantage is obviously 

 a question to be settled later by the majority of 

 constructors, since it is not yet widely adopted. 



With iIk; possible exception of flying at low 

 speeds, it would seem that for longitudinal 

 stability flying machines possess a considerable 

 amount of inherent stability, and only call for 

 serious assistance from the pilot in special circum- 

 stances, as when the aeroplane is struck by a gust. 



Lateral stability, however, receives far greater 

 variety of treatment, and except that all machines 

 provide large control for the pilot, there is, in the 

 machines exhibited, little evidence of unanimity 

 of method. Leaving out the diflicult problem of 

 the spiral di\e and considering the machines for 

 lateral stability in linear motion, the points of 

 interest in the machines rest with the positions of 

 the vertical fins or their equivalents. 



The most usual combination of fins, which may 

 be seen on the Bleriot, Dcperdussin, and Bristol 

 m.ichines amongst others, is a dihedral angle, 

 between the wings, constituting an equivalent fin 

 above the centre of gravity, and the side of the 

 covered body together with the rudder, the latter 

 making :i fin behind the centre of gravity. In a 

 recent lecture before the Aeronautical Society, the 

 superintendent of the Aircraft h'aclory pointed out 

 llial Ihe elTecl of dihedral angle is dependent lo 

 a greater or less extent on the air.mgenu-nt lor 



