124 F. OMORi : 



II. 



4. The building, in which my Horizontal Pendulums have 

 been set up, is a brick '* Earthquake-proof House, "^ erected in 

 the grounds of the University (Hongo, Tokyo) by the Imperial 

 Earthquake Investigation Committee, as a sort of a seismological 

 observatory. (See fig. 5.) The structure, which covers an area of 

 83 sq. m., simply consists of four walls of parabolic section 

 covered with a tiled roof furnished with a skylight, each wall 

 being 5 ^ ni. high, 0.7 m. thick at toj) and 2.4 m. thick at the 

 ground level. The entrance is the only opening in the walls. 



The house, thus forms a kind of a stout hollow column, 

 and its walls, from which the Horizontal Pendulums are suspend- 

 ed, may be considered to be unaôected by the direct impact 

 of winds. 



5. My Horizontal Pendulums for recording earthquakes 

 and other earth movements mechanically and continuously, are 

 constructed on the principle of keeping the heavy mass com- 

 paratively small and reducing friction to a minimum. As each 

 Pendulum records only the motion normal to its plane, we want, 

 for the complete observation of earth movements, a pair of 

 these machines to be placed at right angles to each other. 



The reference letters aj^ply to PL II, which illustrates the 

 mechanical details of one of the Horizontal Pendulums, fig. 1 

 and fig. 2 giving respectively side and front elevations. 



The Pendulum consists of a thin brass cylinder, a, filled 

 with lead, 16 cm. in height, 10 cm. in diameter and about 14 

 kgm. in weight, attached a little above its centre of gravity to 



1. Designed by Prof. K. Tatsuno, meiuber uf the lauperial Earthquake Investigation 

 Committee. 



