4 Art. 9.— T. Terada : 



on account of its remoteness from any powerful electrical plant^^ and 

 also for the conveniences which its proximity to the Marine Labo- 

 ratory afforded. The edge of the terrace overlooking the bay was 

 partly cut ofï to form a vertical cliff. An underground room was 

 then excavated with a narrow entrance (Fig. 1, Ei) opening at the 

 foot of the clifï. Since the rock was entirely of a soft tertiary forma- 

 tion, the excavation was comparatively^ easy. The approximate size 

 and the arrangements of the room may be seen from Fig. 1. A is 

 the antechamber where the photographic recording apparatus R and 

 the acetylene lamp L used as the source of light, were installed on 

 the pedestal Pj or Pa. In the interior chamber B, communicating 

 with A by the narrow entrance Eo and also by the windows Wi 

 and Wo, two long pedestals P3 and P4 are laid for mounting the 

 magnetic instruments. Ci, Co and Co are small stone pillars on 

 which were fixed the stands for fitting the magnetic bar used for 

 determining the sensibility or constant of the magnetographs. 



In the beginning of the observation, two similar sets of 

 instruments were arranged on Pi P3 and Po P4 respectively and run 

 simultaneously. The results were almost identical, as was to be 

 expected, and the later part of tlie observations was almost 

 exclusiveh" made on pedestals Pj and P3. 



The temperature of the interior chamber was kept tolerably 

 constant, the daily variation amounting to only a fraction of a 

 degree and the annual range scarcely reaching 3°C. 



A serious difficulty met with was, however, the extreme 

 dampness of the chamber during the summer months. Not only 

 does the moisture of the external air, saturated at very high 

 temperature, gradually condense in the cooler interior, but 

 luimidity is constantly supplied by the percolation of underground 

 water, tlirough numerous fissures in the wall and ceiling, fed by 

 the abundant rain during " Baiu,'^ the rainy season on our entire 

 Pacific coast in early summer. This caused so much trouble that 

 during a certain period observations were almost rendered im- 

 possible. Though it was not impossible to overcome this difiiculty, 

 the funds at our disposal were not sufficient to carry out the 



1) The nearest tramway line is at Kamakura, nearly 20 km. N. from the station. 



