MAGNETIC SURVEY OF JAPAN FOK THE EPOCH 1895.0. 7 



which iron was replaced. The result verified to a certain extent 

 the selection of the station. Local disturbances in an apparent- 

 ly smooth plane were sometimes surprising. Those points are 

 not numbered in the list but are given as " Syuttyo "; Nos. 54 

 to 61 in the first year are of this category, and they would have 

 been so named had they not been observed with the express 

 view of finding the effect of Huzi. 



§ 4. Instruments. 



There are four sets of magnetometers belonging to the Earth- 

 quake Investigation Committee, three of which were used in the 

 survey. Their construction is the same in principle as that 

 adopted in the magnetometer used by the South Party of the 

 magnetic survey of 1887, and fully described in Vol. II p. 178 

 and Vol. V p. 163 of this journal. The plate in the front page 

 is the photograph of No. 1 instrument. The theodolites were 

 ordered from Troughton and Simms of London for the special 

 purpose. The graduated diameter of the azimuth circle is 18 cm. 

 and that of the altitude circle 17.5 cm., both are divided to 

 every 10' and are read with two verniers to 10". The telescope 

 is of 4.8 cm. clear aperture and 36 cm. focal length and has 

 five transit wires of about 10*^ equatorial interval. 



The modifications now introduced in the part of magneto- 

 meter are of minor importance being simply for the convenience 

 of manipulation, they are : — 



1. The magnetometer which is now put in a metal tube 

 to guard against electrostatic effect of glass tube. 



2. Magnetometer stand which is in the form of a tube 

 standing upon three legs and can be fixed either to the base 



