HERMANN VON HELMHOLTZ 



signalling the moment of the transit of a star, there 

 were slight differences in the observations made by 

 equally competent observers, differences apparently 

 due to individuality. It is said that Maskelyne dis- 

 missed an assistant because, in making observations, 

 he was always behind his master in point of time. 

 Bessel was the first to recognise that the discrepancies 

 were due to the fact that men feel and even think at 

 different rates. As Hermann points out, the coinci- 

 dence is striking that years afterwards, in the very 

 university where Bessel worked, Helmholtz showed 

 that there was a physiological basis for his conjecture. 

 Psycho-physical investigators of later times, with im- 

 proved appliances, have measured the time occupied 

 in reflex actions, and even in those psychical operations 

 involved in choice, discrimination and volition. Many 

 ingenious instruments have since been devised, but 

 the root idea of them all may be traced back to those 

 experiments of Helmholtz, which originated the 

 methods of the psycho-physical school of investigators. 



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