ox TflK EAKTHQUAKE AXD VOLCANIC PHENOMEXA OF JAPAX. 107 



tion of moisture from and upon various natural surfaces, but I have not 

 been able to consult them. 



In open ground 30 per cent, of the rainfall may percolate, but in a 

 forest as much as 80 per cent, may find its way downwards, the difierence 

 being due to evaporation ; but as evaporation may cease or even be re- 

 presented by condensation during the night, it would seem that the volume 

 of water in surface wells especially on hot days following rainy weather 

 might have a daily fluctuation. Such a fluctuation would, however, only 

 account for the rising of water during the night and for an additional rise 

 about midday. 



Another point to be noted is the fact that the alternations of evapora- 

 tion and condensation mean that neighbouring areas, some of which are open 

 and others covered with forest every 12 hours, are unequally relieved of 

 considerable loads. For example, from an area of about 140 feet square in 

 front of my house, which faces south, every day during fine weather about 

 5 tons of moisture are removed. JTrom the back of the house, which is 

 sheltered from the sun, and where the ground is always damp, compara- 

 tively but little is evaporated. The underground chamber is sheltered by 

 a grove of trees on its south and west sides, and on the east side it is open, 

 and pendulum E behaves as if a load were removed from the east side 

 during the morning and afternoon, and that side of the ground had con- 

 sequently risen. Pendulum A in my house, where there is an evaporation 

 area on the east, south, and partly on the west side, usually behaves 

 like E, to which, however, it is at riglit angles. 



By comparing the table of daily waves with the rainy days when there 

 was no sunshine, when it may be assumed that evaporation was small, as, 

 for example, between March 8 and 11, it will be observed that the daily 

 curves for A and E were not measurable. On sunny days, even if it 

 rained, the curves were pronounced, but they were also large on other days, 

 when, however, evaporation may possibly have been great. 



To settle this question future diagrams must be compared with the 

 records obtained from a hygrometer exposed to the open or by two pen- 

 dulums in parallel positions, but on the opposite sides of a piece of forest 

 land. Two pendulums thvis placed ought at the same time to move in 

 opposite directions, that is, during the day each boom ought to move 

 towards the forest. 



An observation entirely opposed to what is here suggested is that made 

 by Professor Kortazzi at Nicolaiew, who placed a hydrograph in the 

 cellar where a horizontal pendulum was established, and found that the 

 diagrams given by the two instruments were very similar. This he 

 attributed to the stone column carrying the pendulum behaving like a 

 sponge and absorbing moisture. When the openings to the cellar were 

 closed and the pillar covered with a waterproof material the effect of 

 moisture almost entirely disapjjeared. 



(t)i) Effects produced by emptying a Well. 



To determine what eflfect a slight disturbance of subterranean water 

 would produce on a horizontal pendulum, on May 21 I employed men to 

 rapidly empty a well which is 104 feet distant in an E.IST.E. direction from 

 pendulum A. The well is 42 feet 7 inches deep, 2 feet Tinches in diameter, 

 and on this particular day it contained 13 feet 1 inch, or about 2 tons of 

 water. 



