30 FALK— ELECTRON CONCEPTION OF VALENCE [April 24, 



extends the classification, and since much of the classification de- 

 pends upon a number of correlated facts and relations and not upon 

 single crucial and well-defined experiments, it may be expected that 

 some of the formulas advanced and explanations of reactions offered 

 at the present time will be subject to change. Caution must contin- 

 ually be exercised against reading into valence structures ideas which 

 are foreign to valence. A limitation of the questions discussed to 

 the phenomena which may rightly be included would obviate much 

 confusion and bring valence relations into clearer light. 



Harriman Research Laboratory, 

 Roosevelt Hospital, New York. 



