PREFACE. VU 



The iippearance of tlio volume was mueli delayed by various 

 eiicuuistances under wliieli the writer had to work. lu the 

 course of the preparation he had to make two official trips to 

 Europe and to take a half year's rest between those tw^o on ac- 

 count of his health, beside having had to attend several unavoid- 

 al)le committee works. But above all we regret the delay in 

 lithographic printing which kept the work over three years. The 

 publication however is quicker than otherwise it would have 

 been through the kind assistance of his colleague Prof. H. 

 Nagaoka who arranged the materials of the appendix and com- 

 menced printing during his absence. 



A. Tanakadate. 



Physical Laboratory, 

 Imperial University, Tokyo. 



March, 1904. 



