ELECTRICAL AND OTHER FACTORS 255 



cally by jarring or bending or by scraping with a piece 

 of glass; summation effects are a conspicuous future of 

 this form of activation; a single scrape or blow, or a suc- 

 cession of these at infrequent intervals, being usually 

 ineffective, while several scrapes in rapid succession cause 

 typical activation. Chemical activation may be shown 

 by the appucation of a reducing agent Uke sugar. The 

 same kind of effect is produced in the wire, whatever the 

 method of activation, the local change simply initiating 

 a propagated effect whose nature and extent depend 

 on the special conditions existing in the metal-electrolyte 

 system. There is here an evident analogy with explo- 

 sions or other kinds of ^'trigger effects.'' Hence the 

 system, when in a fully transmissive state, behaves in 

 the " all-or-none " manner. 



In reality electrical activation is illustrated in all 

 these cases, even when the local alteration initiating the 

 reaction is mechanical or chemical; i.e., the electrical 

 factor is the essential one in the transmission of the 

 effect. The special conditions of electrical activation 

 are, however, best shown by a somewhat different kind 

 of experimental arrangement. Two passive wires, placed 

 parallel one or two centimeters apart, are immersed in 

 a vessel containing dilute HNO3 and are connected by 

 wires and an open key to a battery (e.g., of about 2 

 volts E.M.F.). When the key is closed, the cathodal 

 wire (that connected with the negative pole or zinc of 

 the battery) is at once activated, while the anodal wire 

 remains unchanged. This experiment shows that activa- 

 tion is a polar effect and dependent on cathodal reduction. 

 Activation also requires a certain minimal E.M.F. in the 

 battery, usually exceeding one volt, and a certain minimal 



