44o 



NATURE 



[September 28, 191 1 



In order to extend the premises to cover a plausible 

 expression foi the resistance to flight and power expended, 

 it was necessary to adopt a value for skin-friction. A; 

 t Zahm's formula was adopted, but the matter needed 

 further research. Skin-friction was of such fundamental 

 importance in aerodynamics that it was imperative lo put 

 it upon an accepted basis analogous to the position occupied 

 by normal pressure. The coefficient of night, representing 

 the resistanci pel unit load, might be shown to be inde- 

 pendent of speed, and to depend on the angle of the 

 plane, and, further, to have a minimum value depending 

 on the coefficient of skin-friction. 



On the present hypothesis the minimum coefficient of 

 flight obtained with planes of a very small effective angle — 

 about 5 — such as would necessitate flying at much higher 

 speeds than had hitherto been realised. The existence of 

 an angle of least resistance was very important in connec- 

 tion with tin problem of variable speed machines. Body 

 resistance in a practical aeroplane was a supplementary 

 resistance to that of the planes, and should always be 

 considered as such. 



Turning to the question of stability, in practical aero- 

 planes natural stability, both longitudinal and lateral, was 

 mainly based on the principle of the dihedral angle. The 

 acentric centre of gravity, in which the principal masses 

 were placed well below the centre of pressure, was fre- 

 quently suggested as a stabilising influence, but the per- 

 manent existence of a couple between the centre of gravity 

 and the centre of pressure indicated liability to pronounced 

 oscillation and did not find general favour. 



Apart from the question of stability, progress in flying- 

 machine design was mainly a problem of increasing the 

 'Mi, iency of the machine. The need for further information 

 on such subjects as the effective angle of the plane, sweep, 

 skin-friction, and other similar problems that come within 

 the province of research work in physical science, was 

 all-important. If the aeroplane of the future was to carry 

 heavy loads and to fly far and fast, it needed to be more 

 efficient than the aeroplanes of to-day. 



Dr. W. N. Shaw, who followed, spoke of the dangers to 

 aviators that lay in the constant fluctuations in the speed 

 and direction of air-currents, and pointed out that over sea 

 the oscillation of the wind speed was generally less than 

 that over the land. 



Prof. Petavel discussed the various suggested means of 

 obtaining stability from the practical aviator's point of 

 view, and stated his opinion that, given an aeroplane with 

 a fair proportion of natural stability, the experience and 

 control of the pilot might be very well left to supply tie 

 rest. 



'The subject of motors was broached by Mr. Beaumont, 

 who said thai, so far as the engine itself was concerned, 

 it was very questionable whether any great increase in 

 filler the mechanical or dynamic efficiency could be made: 

 and Sir William White, in the course of some general 

 remarks, stated that the question of propeller efficiency 

 must be dealt with, as in the case of ships, experimentally, 

 bv means of models. 



THE INSTITUTE OF METALS. 



I ill innual autumn meeting oi the Institute of Metals 

 was held at Newcastle-on-Tyne on September 20-22. 

 The I. ool Mayor (Sir W. H. Stephenson), in offering a 

 welcome to the institute, said thi institute has made sub- 

 stantial progress with tin- objects it lias in view, to serve 

 the industries connected with the non-ferrous metals in a 

 similar manner to that in which the Iron and Steel 

 Institute has erved thi iron and steel trades. Research 

 work to meet the needs of industrial development is clearly 

 I. Such work is constantly in progress at the 

 National Physical Laboratory and in the universities and 

 the university colleges. The Institute of Metals affords a 

 means of communication among the many workers in the 

 field covered by its activities, and the knowdedge acquired 

 by research can thus be applied to practical work. An 

 important research which illustrates the services which 

 such an institute may render is being carried out by the 

 -ion Committee. Sir Gerard Muntz, in acknowledg- 

 ing the welcome, referred to the research on the causes of 



NO. 2187, VOL. 87] 



corrosion in condenser mho,. He said that a plant which 

 should imitate as closely as possible the condition 

 ing in a marine condenser is being erected at Liverpool, and 

 will be ready for inspection and testing in a few wceka. 

 It is intended to investigate the conditions obtaining under 

 Admiralty and commercial conditions, and it is believed 

 mat a large number of the baffling problems connected with 

 corrosion can be investigated adequately. Generous assist- 

 ance has been given by the University of Liverpool, but 

 additions to the research fund are urgently needed, as the 

 work, to yield useful results, must extend over a period of 

 two or three years. Several papers were afterwards read 

 and discussed, and the following brief summaries will{ 

 indicate their scope. 



Mr. J. L. Haughton and Prof. T. Turner contributed a . 

 paper on volume changes in the alloys of copper with tin. 

 The work described is a continuation of previous n 

 on the changes in length which occur in a cast bar during . 

 and after solidification. The method employed has been ! 

 that of applying an extensometer to one end of a cast bar I 

 while the other was kept fixed. The apparatus employed | 

 has been modified in order to allow a single operator to 

 observe both pyrometer and extensometer readings at the I 

 same instant, and to record these results by means of a J 

 chronograph on a paper tape. There are four maxima in 

 the expansion curve, and three of these, with about 10, 

 46, and 65 per cent, of tin respectively, agree with the 

 " crystallisation interval " as determined from the accepted 

 equilibrium diagrams. 



The aim of a paper by Dr. W. M. Guertler, on the 

 electrical conductivity and constitution of alloys, was to 

 direct attention to the property of electrical conductivity in 

 its bearing upon the practical determination of the con- 

 stitution of alloys. The relationship between concentra- 

 tion, temperature, and any given property — electrical con- 

 ductivity, specific volume, magnetism, &c. — is best brought 

 out by the employment of a coordinate system, as in the 1 

 equilibrium diagram. The converse problem is one of great ' 

 importance, viz. that of obtaining the equilibrium diagram 

 (when it is unknown) by projection from these surfaces on ] 

 to the basal plane. The best method for the determina- 

 tion of the equilibrium diagram is known by the name of 

 "thermal analysis." Dr. Guertler discussed the limita- 

 tions of " thermal analysis," and in particular explained 

 why it fails in those cases where, as so often happens in ! 

 practice, a state of complete stable equilibrium is un- 

 attainable within a comparatively short interval of time. 



In a paper by Mr. D. R. Pye, on the mechanical proper- 1 

 ties of hard-drawn copper, the lack of any satisfactory^ 

 definition of standard hard-drawn copper was pointed out. 

 Experiments were described confirming a suggestion made j 

 by Mr. A. P. Trotter that the tensile strength per square 

 inch diminishes with increase of diameter according to a | 

 linear law. It was also shown that the elongation 'at 

 fracture for similarly manufactured wires depends very! 

 much on the diameter, being considerably greater fori 

 larger sizes of wdre. It was suggested that a satisfactory 

 definition of hard-drawn copper wire would fix a minimum 

 tensili strength per square inch given by the formula 



T = 30 — 2oD, 



and a minimum elongation per cent, at fracture given by j 

 the formula 



e = sD, 



where D = diameter in inches. 



In a paper by Mr. George Hughes, on non-ferrous 

 metals in railway work, he placed on record some of the | 

 methods of working, and uses pertaining to, the non-1 

 ferrous metals in locomotive and carriage construction. A I 

 short account of the bearing metals used under tin name 

 of whit, metals was included, together with a note onl 

 non-ferrous metals and alloys used in the railwa l 



department. 



The main object of Mr. C. A. Edwards's paper, onl 

 further notes on the nature of solid solutions, was to deal 

 with points of interest raised in the discussion on 9\ 

 previous paper by Mr. Edwards on the same subject, and 

 to stimulate further discussion. 



The paper by Prof. H. Louis, on the failure of a brazed 

 joint, gav an account of the investigation of tie cause of 



