MAGNETIC SUKVEY OF JAPAN FOR THE EPOCH 1895.0. 5 



dry cells, small electric lamps, a box of necessary tools and 

 materials, besides the "Berliner Jahrbuch," a logarithm table 

 and note books. 



The magnetometer is described in the next section: All the 

 chronometers used were siderial, made by Negus, New York. 

 The tent was specially designed for the purpose, it is round 3.5 

 meters in diameter pitched with a center pole of 2.7 meters 

 length. It is made in two parts, a conical top and a cylindrical 

 wall, each of which can be folded back partly or wholly to 

 accommodate various circumstances. It has a mosquito net fit- 

 ting inside closely throughout. The top can be opened for 

 astronomical observations and turned round after the fashion of 

 an equatorial dome. Observations were often made with the net 

 on, this caused diffraction phenomena producing four images with 

 tails round the central spot, corresponding to square meshes of 

 the net. The effect is however of no importance for the kind 

 of work we are concerned with. On hot days the wall was 

 removed giving the tent an appearance of a large umbrella with 

 hanging curtains. This defence against insects proved also to be 

 a useful guard for the instruments against wind and dust. The 

 tripod for the magnetometer was set on the east side and that for 

 the dip circle on the west, and the sofk on the north ; a small shelf 

 was rigged to the center pole for laying notes and small articles. 



The magnetometer, dip circle and chronometer were carried 

 by the observers themselves in travelling by rail or carriage, in 

 crossing over mountains they were usually carried by coolies or 

 sometimes on horseback ; the chronometer was well corked 

 round the gimbals and the box thickly wrapped in blancket 

 which secured it both against mechanical jars and abrupt 

 changes of temperature. 



