166 



KNOTT AND TANAKA.DATE 



was Oiwake at the base of Asama Yama ; while fully half his stations 

 lay on a route encompassing Fuji Yama. At these latter, however, 

 only the Declination seems to have been measured. The observations 

 bring out very markedly the disturbing effect of volcanoes upon the 

 magnetic cliaract eristics of any district. The horizontal forces 

 measured by Mr. Schutt appear to be on an a\'erage about 2 per cent, 

 greater than the values indicated by the observations of the present 

 survey, — a difference which, surely, must be due to instrumental error. 

 From March 16th to August 20th, 1883, Mr. Wada of the 

 Meteorological Observatory, Tokyo, took complete hourly observations 

 of the Declination. It may be well to give here the mean hourly 

 values during the whole interval of 5 Y(j months. 



The mean value is 4° 16 '.75 and the mean diurnal range is 6 '.93, 

 These hourly observations of Mr. AVada are the most comjjlete and 

 valuable of the kind that have been made in Japan. It may be 

 remarked that within the last few months the same gentleman has 

 got into fair working order a complete set of Mascart's self-registering 

 magnet ographs. Unfortunately they were not ready for use during 

 the months of our survey, so that we have no means of applying even 



