THE DISTURBANCE OF I80MAGNETICÖ. 



175 



place. A\'ith regard to the lines of equal clip the change is least 

 marked. The bending of these lines towards the south are principally 

 caused by tlie value of dip at Isshiki. In passing, we may remark 

 that Isshiki lies very near the now well-known tectonic ridge along 

 which the geological aspect of the country is suddenly changed. 

 Another observation at a station somewhere between Tsu and Yokkaichi 

 mis'lit tell whether this bend exists in the region u'cnerallv, or 

 whether it is of a more local character and peculiar to the southern 

 coast. 



As was stated in the introduction, we can not ascribe these 

 changes solely to the effect of the eartlupiake. without thorough 

 knowledge of the secular vari;iti(jn. JUit the very appearance of these 

 charts is enough to show that they are anything but usual. The 

 most important and interesting Cjuestion that naturally arises will be — • 

 Are these changes of the magnetic state caused suddenly by the eartli- 

 (|uake, or have they been taking place wholly or partly before 

 it ? The only results that we can refer t(j for information about the 

 secular variation, are those of Messrs. Sekino and Kôdari. Mr. Sekino 

 made 13 observations in various places in the close neighbourhood 

 of xsTagoya. About Xagahama and Ubama tliere are no observations 

 until we come to the region near Fukui, ^^■here Mr. Ködari made 7 

 observations. The values of 11 as obtained by these observers are such 

 as to change the course of the lines of equal horizontal intensity in those 

 regions both in the chart for 1<S<S7 and in that given by Dr. 

 Xaumann in his paper : thus in tlie district near A'agoya 11 is .^9, 

 while in [)laces near Fukui, which are 2 or 3 degrees north, the values 

 of 11 a.re nearly .300, sometimes .SO-l. It is difficult to conceive 

 how Ur. Xaumann obtained his lines of e<|ual horizontal intensity 

 as given in his chart, unless he excluded either of these sets of observa- 

 tions. 



