A Magnetic Survey of all Japan 



carried out, 



by Order of the President of the Imperial University, 



by 



Cargill G. Knolt, D. Sc. (Edin.), F. R. S.E., Professor, and 



AikilSU Tanakadale, Assistant Professor of Physics, 



Imperial University, Tölcyö, Japan. 



With Plates VI -XV. 



Prefatory Note: — In tlie Summer of 1887, tlie Im)x^rial Univer- 

 sity of Japan at last saw its wa}' to carry into effect a proposal which 

 liad ])een made l)y me some years previously. Along with ]\Ir. 

 Tanakadate and Messrs. Nao'aoka and Tmag^awa, T was arcordino-]v 

 instructed by the President of the University t<^ make a Magnetic 

 Survey of all Japan within, if possible, an interval of two and a hall 

 or three months. 



I regret exceechngly that in the preparation of the account which 

 follows [ have not had the continued assistance of ^Iv. Tanakadate. 



Before setting' out f )r Scotland in January of this year, however, 

 that gentleman left his own observations all but reduced, along with 

 a hdl account of his instrumeiits and modes of operation. This 

 account is reproduced, very inuch in his own words, in Section III of 

 the present paper. That Section, therefore, is peculiarly Mr. Tanaka- 

 date's contribution. For the rest — the combining of the observations 

 by the method of Least Squares, the preparing of the Charts, etc. — 



