179 
investigation, have been found to entirely conform to the theory or to 
require only minor modifications, that we hesitate to accept such a sweep- 
ing statement as that contained in Shinn’s paper. The facts cited do not 
necessarily conflict with the theory—indeed, they would seem to point to 
the truth of the theory. What is needed is more experimental evidence 
covering these points. 
Purdue University, 
Lafayette. Ind. 
