﻿604 Dr. R. S. Willows on the 



An analysis of Mr. Marconi's numerous polar curves in 

 the light of this explanation shows that we have E.M.F. (1) 

 = E.M.F. (2), as it should be, and that in the case of the 

 various bent receiving antennae used by him E.M.F. (3) is 

 from one to four times E.M.F. (2). 



In conclusion I wish to mention my obligations to my 

 Assistant, Mr. G. B. Dyke, B.Sc, for his willing and 

 energetic as well as intelligent assistance in the above 

 described work. The measurements not only required 

 accurate observations and care to avoid various sources of 

 error, but necessitated a large amount of active exercise in 

 going to and fro between the stations mostly taken in very 

 hot weather. 



LXX. Electrical Resistance of Alloys. 

 By R. S. Willows, M.A.,"l).Sc* 



THE experiments of Fleming and Dewar f and others 

 have shown clearly the wide differences between the 

 electrical properties of alloys and of the pure metals com- 

 posing them. The well-known investigations of Matthiessen 

 show that the resistance of alloys containing two of the metals 

 lead, tin, cadmium, or zinc, and no other substance, can be 

 calculated from the resistances of their constituents, when 

 the proportions present of each metal are known. The 

 specific resistance of all other alloys is greater than would be 

 given by a calculation based on the assumption that the 

 components conduct proportionally to the volume of each 

 present. This gives rise to the curious fact that the addition 

 of pure silver (a good conductor) to gold (a worse conductor) 

 decreases the conductivity of the latter. Fleming and Dewar 

 have also shown that the resistance of pure metals decreases 

 very greatly as the absolute zero is approached, while alloys 

 still retain a great part of their resistance. 



Lord Rayleigh J has advanced a theory, intended to account 

 for these differences, which is based on the thermo-electric 

 properties of a mixture of two metals. Liebenow §, in various 

 publications in Germany, but at a later date, has advanced a 

 theory which, physically, is identical with that of Rayleigh. 

 (I might mention that in German publications the theory 

 is always referred to as Liebenow's ; Lord Rayleigh's 

 contribution seems to have escaped notice.) 



* Communicated bv the Physical Society : read November 23rd, 1906. 



t Phil. Mag-. [5] vol. xxxvi. p. 271 (1893). 



X Scientific Papers, vol. iv. p. 232. 



§ Encyklopcidie der Elektrochemie, Band 10. 



