Changes ^produced in Matter hy Electi^ic Waves. 455 



C. On the physico-chemical changes produced in a sensitive sub- 



stance by the action of electric radiation, and on the radiation- 

 product. 



D. The phenomena of electric reversal and of radio-molecular 



oscillation. 



E. On "fatigue" and the action of mechanical tapping and other 



disturbances by which the sensitiveness of a fatigued receiver 

 may be restored. 



F. On the nature of the passage of electricity through imperfect 



contacts, and the influence of various physical agents on the 

 cui'rent. 



Ct. On the systematic study of the contact-sensitiveness exhibited 



by metals, non-metals, and metalloids. 

 H. On the contact-sensitiveness exhibited by alloys and compounds. 



I intend to treat the above subjects in some detail, and in the 

 present paper will especially deal with the first five lines of investiga- 

 tion. These, it -is hoped, will afford an explanation of some of the 

 most perplexing anomalies. All the subjects mentioned above are 

 more or less interdependent, but their treatment in one paper would 

 make the subject very complicated. It would be easier to take a 

 more generalised and complete view of the subject as a whole, after 

 each of the above-mentioned inquiries has been separately considered. 

 With reference to the flow of electricity through imperfect contacts, I 

 need only mention here that the phenomenon seldom obeys Ohm's 

 law. In many instances the phenomenon appears more allied to the 

 discharge of electricity through a gaseous medium. 



Mass Action and Molemlar /Idion. 



Of the attempts made to explain the action of contact-sensitiveness, 

 Professor Lodge's theory of coherence has been the most suggestive. 

 The coalescence of water and mercury drops in Lord Eayleigh's 

 experiments, and Professor Lodge's observation of the welding of two 

 metallic spheres by powerful oscillatory discharge in the neighbour- 

 hood, apparently lend much support to the theory of electric welding, 

 which explains in a simple manner the diminution of contact-resistance 

 of various metallic filings when subjected to strong electric variation. 



On this theory it follows that all imperfect contacts should exhibit a 

 diminution of resistance when subjected to electric radiation. In 

 carrying out a systematic investigation of the contact-sensitiveness of 

 metals, I, however, found that there are substances, of which potassium 

 may be taken as a type, which exhibit an increase of resistance. 

 Potassium is not a solitary instance ; I have found a large number of 

 elements exhibiting this action; the number of compounds which 

 exhibits a similar action is also considerable. Other, experiments will 



