MAdN'ETK SllJVKV oV .lAl'AN. l<iî^' 



December I^itli. Tlic i)l)serv;iti<)iis were iiia<lc (i>ii:ili\" aboul D a.m. 

 or 8 p.m.. Iiiil Hot with aljsolute reii'iiJarity. Tlins to iii;ikc tlie 

 results comparable amongst themselves, corrections due t(j the diurnal, 

 annual, and secular \ -ariations ought t') lie applied. 01' tlie.>?e the 

 diurnal variation is the one which will tell most in the eireumstances ; 

 but I am not aware if any attempt has been made to reduce :dl t\\r 

 observations (especially of the declination) to one hour.* 



Considerinu' then the manner in wliich Sekino's survev \va.^ 

 carried out, we are 1 think justilied in regarding the observations as 

 an insufficient basis for any safe generalization. 



It thus a[)peared th;it the thing to be desired was a new survey — 



what might be called a ])reliminary survey of all dapan. special 



attention to be paid to the distribution of stations, and the whole to 



be completed within its short a time as possible. The scheme tinall\- 



decided upon was brietly as follows: — To form two parties, the one 



or Northern Party to survey the northern and eastern parts of Japan, 



includinof some stations in the Island of Yezo. the other or Southern 



Party to survey the south-western parts including one or more 



stations in Korea. This required two sets of instruments. Already 



the University })ossessed the ordinary Kew l^ortaljle Alagnetometer ; 



and with this the Northern Party conducted their sur\ev. The 



Dipping Needle used by the Northern Party was loaned by the Koy;tl 



Society Committee: and I take this 0]>portunitv of cordially tluiidvinu" 



them for their kindness to me personally as well as t(j tlie Imperial 



University of Japan, in the work of rhe northern party 1 was ably 



assisted bv Mr. H. Na^aoka, »jne of the graduates of the year. 



* There .seems to be a slight iuaccuraey iu Dr. Nanmaun's'remarks (See page 8 of the paiu- 

 phlet) ou the reJiictioa of these observations to oue hour. I uuderstauil fruui Mr. Sekiim 

 Unit uo diurnal correction was applifil to the observations made at tbc northern station^ 

 (Aoniori and Iwanmna being excepted). At the southern stations corrections were applied in 

 accordance with the three-hourly observations that wtre being made iu Tokyo at Ibe time, 

 llic observations being reduced to the mean ot the 'J a.m. iiud '■> p.m. oli>ei vation>. 



