FIRST RESEARCHES IN PHYSICS 53 



vaster spectrum, of cosmic radiation ; witness the additional 

 octaves of shorter and shorter ultra-violet (photographic) 

 rays, and corresponding octaves of heat-waves longer than 

 the lowest visible red. But now far below these heat-rays 

 of the great spectrum, large by comparison with those of 

 light (which range from 60,000 to 25,000 to the inch), Hertz 

 had experimentally produced new rays altogether, whose 

 existence, and to some extent therefore their light-wave-like 

 behaviour, had indeed been foreseen by Maxwell ; yet with 

 strange and varied properties he had not foreseen, and soon 

 capable of applications which would have surprised and 

 delighted him as much as any. To realise the enormous 

 magnitude of Hertz's waves, as compared with those of 

 the longest heat-rays known, we. must leave their scale, that 

 of known ether- waves hitherto, and compare them with the 

 big waves of sound, slow-moving through our atmosphere, 

 -a heavy and viscous fluid unlike the imponderable and 

 elastic ether. Taking, then, the ordinary velocity of sound 

 in warm weather at 1200 feet per second, and the range 

 of audible vibrations at from 16 per second for deepest 

 note and 30,000 for highest a wide range of no less than 

 ii octaves we have about 70 feet for the largest and 

 lowest appreciable sound-waves, and say 4 inches for the 

 shortest and highest. But even Hertz's shortest waves 

 when measured turned out to be about 4 yards, and his 

 longest waves ranged to hundreds of yards, while evidence 

 was soon forthcoming that this immense electric spectrum 

 could be extended in both directions, not only shortening 

 towards the heat spectrum, but lengthening also to an 

 unknown immensity of magnitude. 



But Hertz, while thus triumphantly vindicating Max- 

 well's main life-labour, was still only at the opening of the 

 full verification necessary. Given these electric waves, 

 even with their enormously longer wave-length than light, 

 must they not behave like light ? If so^ one would expect 

 them, in the first place, to be variously transmissible i.e. 

 some bodies should be transparent to them, some absorbent 



