72 LIFE AND WORK OF SIR JAGAD1S C. BOSE 



unexpected and perplexing result that it had become 

 insensitive once more. This particular insensitiveness 

 could not, as in the case of fatigue, be restored by further 

 rest ; but he excited the ' idle ' receiver by an electric 

 shock, with the surprising result that its sensitiveness was 

 restored. Two altogether different treatments were thus 

 found necessary in the two cases : rest for the ' fatigued ' 

 receiver, and active stimulation for the ' idle * one. 



The theory of the ' Coherer ' was therefore inadequate ; 

 for if the diminution of resistance by external stimulus 

 were brought about simply by soldering of particles, such 

 diminution would be independent of the previous history of 

 the receiver, i.e. of its moderate rest, restoring sensitiveness 

 as if from fatigue, or of its prolonged rest, reducing this as 

 it were to idleness. 



To explain these anomalies, Bose was led into 

 new and wide fields of investigation. Hence two 

 papers. 1 The terms ' Electric Touch,' or ' Contact-sensi- 

 tiveness/ were introduced to avoid the theory involved 

 in the term ' Coherer/ and also because the nature of 

 response depended on the surface of contact, and not on 

 the substratum. An insensitive metal such as copper, 

 when coated with a thin film of a sensitive metal like 

 cobalt, acquired extreme sensitiveness : whereas a highly 

 sensitive material like iron, when given a coating of an 

 insensitive metal like copper, gave little or no response. 

 Bose next embarked on a systematic investigation of the 

 contact-sensitiveness of all the metals, non-metals and 

 metalloids obtainable. Many of the rare metals were at 

 the time not available, but in some cases he isolated the 

 elements from their compounds in an electric furnace ; 

 and experimentally overcame many other difficulties 

 encountered at every step. 



The investigations on metals were carried out in the 



1 ' On a Self-Recovering Coherer/ Proc. Roy. Soc., 1899. ' On Electric 

 Touch, and the Molecular Changes produced in Matter by Electric Waves,' 

 Proc. Roy. Soc., 1900. 



