0^' THE EARTHQUAKE AND VOLCANIC PHENOMENA OF JAPAN. 135 



is not likely that pronounced movements would bo recorded upon rock, 

 iieitlier sliould there be an appreciable trace of diurnal waves ou days 

 when it was wet or cloudy. 



2. Contraction due to Desiccntion. —If the desiccation due to heating 

 l^y the sun is followed by contraction, we should expect that during the 

 <lay a pendulum would move towards the side losing the greatest amount 

 of moisture ; that is to say, its movement would be in a direction opposite 

 to that accompanying the removal of a load due to evaporation. On 

 ground covered by trees or buildings, or on ground uniformly open all 

 round, but littrle motion should be expected. Whatever effect was observed 

 it is not likely that it would penetrate many inches beneath the surface. 



The following is a comparison of these considerations, with the 

 observed movements of the various pendulums and the character of the 

 surrounding ground. 



For 100 yards to the east and west of A the ground is equally open. 

 The most open ground, however, lies to the east. It would therefore be 

 ■expected that movement during the day due to unloading would be west- 

 wards. The observed movements, however, although generally westwards, 

 showed too many irregularities, and were too feeble to justify a conclusion 

 that they were due to such an influence (tig. 6). 



For 100 yards round station J the ground is more open upon the 

 western side than upon the eastern side, and the westerly motion might 

 therefore be attributed to desiccation and contraction upon this side. 

 Beyond this limit, however, the ground is most open upon the eastern 

 side, which might therefore, by evaporation, rise. This would give a 

 westerly motion (tig. 7). 



Fig. 8. 



J8 



K.— Moves west from 6 A.M. to 3 or G r.M. 

 12 fi 6 s Noon if IS IS 12 



For 100 yards round K the ground is most open upon the eastern side, 

 and desiccation would result in an eastern displacement. The westerly 

 motion recorded seems to find its only explanation in the fact that the 

 eastern side of the instrument is more open than the western side, but 

 the reason that these movements were greater than those at J is not 

 clear (fig. 8). 



Immediately to the west of R there are tall trees and a deep cutting. 

 So long as the sun shines over these trees upon an area 50 or 100 yards 

 long to the east of the instrument, the pendulum mo^ es towards the area 



