WILHELM HITTORF {1824-1914) 

 WILLIAM CROOKES {1832-1919) 



Just as Galvani, eighty years previously, had been able to 

 draw forth a new phenomenon from the inexhaustible riches 

 of nature, a phenomenon which, not again forgotten, led to 

 the development of quite new and undreamed of fields of 

 knowledge, so did Hittorf and Crookes also follow up the in- 

 vestigation of processes which, up till their time, being out- 

 side the frame of science as ordinarily taught, had been 

 simply regarded as curiosities, which could not otherwise be 

 investigated. The phenomena were those connected with 

 the discharge of electricity through rarefied gases. The pro- 

 cesses had been known since Guericke invented the air 

 pump and the electrical machine; Faraday, who later pro- 

 duced in the induction apparatus a still more suitable source 

 of high tension electricity, had also observed these extremely 

 curious phenomena, with their beauties of form and colour, 

 which fill a space in which the pressure of the air is suffi- 

 ciently reduced, when an electric discharge passes through 

 it. It was also readily possible to follow the gradual transi- 

 tion from the simple short sparks exhibited at atmospheric 

 pressure - which Leibniz was the first to see - to the exten- 

 sive and complex phenomena which occur as the air pressure 

 is gradually reducJed. However, the maze of phenomena 

 which occurred gave no indications of a way which might 

 lead to an understanding of them. 



Hittorf and Crookes were the first to find this way, by 

 selecting from the mass of interlinked but incomprehensible 

 processes a single one, and making it the subject of a special 

 investigation, the example chosen being one distinguished by 

 a certain simplicity. This was a process connected with the 

 negative pole of the discharge - the cathode, as we say here 

 as well as in the case of electrolytes - which had the effect 

 of a radiation proceeding in straight lines from the surface of 



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