ON THE EARTHQUAKE AND VOLCANIC PHENOMENA OF JAPAN. So 



(a) 2'he Instruments. 



Although pendulums made of pieces of aluminium wire and held up 

 ■with quartz fibres with their mirrors and lenses have given excellent 

 results, the apparatus required good installation and careful manipulation. 

 As tliese requirements were not obtainable, excepting in Tukio, before 

 commencing observations in the country my first task was to design an 

 instrument of a simple character, not easily put out of order, and which 

 would give continuous records for at least one week. This was done, and 

 as the six instruments which have been made have worked satisfactorily 

 I give the following desci'iption of one of them. 



Fig. 1. 



The pendulum stand A, fig. 1, with its upright, which is 50 cm. high, is 

 of one piece of cast iron.^ The distancebetween the levelling screws work- 

 ing in brass sockets is 23 cm. The back screw tilts the upright and gives 

 the required degree of stability to the pendulum ; one of the lateral screws is 

 used in adjusting and calibrating the pendulum. It carries a pointer 

 moving over a graduated arc. By turning it, for example, one degree, which 

 means raising this corner of the instrument 3];^ of a millimetre (the 



' The form of the bcd-pli.tc is that of a right-angled triangle with the right 

 angle near A. 



