THE PRESIDENTIAL ADDRESS 15 



disposed to refuse are become head-stones of the corner. In the 

 architecture of the elements they fill places that are distinctive and 

 all-important ; they mark the systematic sequences of the periodic 

 law. In a metaphor appropriate to atomic physics we may describe 

 them as coy ladies with a particular symmetry in their crinoline of 

 electrons, unresponsive to advances which other atoms are ready 

 to make or to receive. Inert though they be, they have found 

 industrial uses. Helium fills airships ; argon fills incandescent 

 lamps ; and neon, so modest a constituent of the atmosphere that 

 you might think it born to blush unseen, has lately taken to blushing 

 deliberately and even ostentatiously in the shop-signs of every city 

 street. In the field of pure science it was neon, outside the radio- 

 active elements, that first introduced us to isotopes. And helium 

 has a greater glory as the key to radioactive transformations and 

 historian of the rocks. Disciples of evolution should be grateful 

 to helium for delivering them from the cramping limits of geological 

 time which an earlier physics had mistakenly imposed. 



My own recollection covers many surprises that are become 

 commonplaces to-day : the dynamo, the electric motor, the trans- 

 former, the rectifier, the storage battery, the incandescent lamp, 

 the phonograph, the telephone, the internal combustion engine, 

 aircraft, the steam turbine, the special steels and alloys which 

 metallurgists invent for every particular need, wireless telegraphy, 

 the thermionic valve as receiver, as amplifier, as generator of electric 

 waves. To that last we owe the miracle of broadcasting. Who, 

 a generation ago, would have imagined that a few yards of stretched 

 wire outside the window and a magic box upon the sill should 

 conjure from adjacent space the strains of Beethoven or Bach, the 

 exhortations of many platforms, the pessimism natural to those who 

 forecast the weather, and the optimism of orators who have newly 

 dined ? 



' Sounds and sweet airs, that give delight and hurt not. 

 Sometimes a thousand twangling instruments . . . 

 And sometime voices . . . that, when I waked, 

 I cried to dream again.' 



I don't know any product of engineering more efficient than that 

 magic box. It needs no attention ; it is always ready for service ; 

 and when you tire of it you have only to switch it off. A blessing on 

 it for that ! Heard melodies may be sweet, but those unheard are 

 often sweeter. Do you ever reflect, when you pick and choose 

 among the multitude of airs and voices, or shut out all from your 

 solitude of thought, that they are still there, physically present, 

 individual, distinct, crowding yet not interfering, besetting you 

 though you do not perceive them, silent until you determine that 



