THE SPIRIT-RAPPERS 



four thousand miles per second eight times around 

 the earth while you say "Ah!" A nerve - wave 

 only travels about a hundred feet per second, so 

 that if you are five feet high and can count ten in 

 one second, the sensation of your foot being sharply 

 pricked can only travel up to the brain and the 

 response thereto travel back again in the time you 

 are counting one that is, a distance of ten feet. If 

 we could think with the rapidity of light, life would 

 seem to us about 1800 times as long as it does now. 



Such are the general conditions of nervous, or 

 "mental," action. The same narrow limitations 

 are true of especial organs. 



The eye and the ear have long been regarded as 

 marvels of mechanism, quite the most wonderful 

 things in the world. But, compared with the im- 

 plements of a present-day laboratory, the sensitive- 

 ness of all human organs seems gross enough. A 

 photographic plate, coupled with a telescope, will 

 reveal the presence of millions of stars whose light 

 does not affect the retina in the least. The mi- 

 croscope too, with its revelations of the world of 

 the infinitely small, tells us how crude, after all, 

 is this most delicate of the senses. Indeed, we 

 may liken it to a piano where only a single octave, 

 towards the middle, sounds. From the ultra- 

 violet to the lowest reaches of the spectrum is a 

 range of some nine octaves of light vibrations, of 



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