406 The Piano-Player — Scientific Aspects [March 10, 



invaluable training in learning to read mnsic, as it involves a degree 

 of precision in assigning the proper length to notes and rests, such as 

 is very apt to be overlooked in the attempt to finger out the notes of 

 a difficult composition on the keys of a piano. 



[O.H.B.] 



WEEKLY EVENING MEETING, 



Friday, March 2(1, 1915. 



The Right Hon. Lord Rayleigh, O.M P.C. D.C.L. LL.D. 



D.Sc. F.R.S., Professor of Natural Philosophy R.I., 



in the Chair. 



Pkofessor Sir J. J. ^Thomson, O.M. LL.D. D.Sc. Pres. R.S. M.R.I., 

 Professor of Natural Philosophy, R.I. 



Experiments on Slow Cathode Rays. 



Electric waves and Rontgen rays are two of the most important 

 discoveries in Modern Physics. Though the two radiations differ 

 so widely both in their properties and methods of production, there 

 is very strong evidence in favour of the view that both are vibra- 

 tions of the same nature as visible light, and that thouo-h the wave 

 length of electrical waves might be long enough to reach across 

 London, while that of Rontgen rays is of the order of the radius of 

 an atom, they were all members of the same family. The question 

 arises whether the very wide gap between these extreme cases is filled 

 up continuously with waves of different kinds, or where there are 

 gaps in this long interval. Electric waves have been produced whose 

 wave length is only a few millimetres, and this limit could no doubt 

 be lowered if special experiments were made with that object ; on the 

 other hand, Rubens has isolated waves in the infra-red spectrum 

 which have a wave length as long as one-third of a millimetre. There 

 is thus no gap between electric waves and light waves. Is this true 

 for the other end of the hght spectrum, i.e. is there continuity 

 between light waves and Rontgen rays ? The shortest wave lengths 

 known for light waves are those discovered by Lyman in what is 

 known as the Schumann region of ultra-violet light. They have a 

 wave length of about one ten-thousandth of a millimetre, while the 

 longest wave length yet measured for Rontgen rays is of the order of 

 one-millionth of a millimetre ; there is thus a gap of about seven 

 octaves between the two. This gap up to the present has not been 

 systematically investigated, but its study promises to be of especial 

 interest. The rays in the Schumann region and very soft Rontgen rays 



