ON THE EARTHQUAKE AND VOLCANIC PHENOMENA OF JAPAN. lO-S 



recorded the motion. The diagrams obtained indicate the following facts. 

 Very shortly after heavy rain the well commences to rise, and the rising 

 continues for three or four days after the rain has ceased. The upward 

 motion, which at times has been as much as 7 or 8 inches in 2-i hours, even- 

 tually becomes slower for about two days, after which the water falls slowly. 

 A more important observation, however, is that during any 24 hours 

 there are fluctuations in the rate of rising or falling which when the well 

 is nearly steady are distinct, but when the coming up or going down of 

 the water is rapid they are barely visible, A number of these daily 

 fluctuations are shown on Plate IV. About midnight and for some hours 

 afterwards the water is at its highest, and it is again high during the 

 middle of the day. It is lowest in the evening and the early morning, 

 which is the time when the greatest quantity of water is being drawn 

 from wells throughout the city. The nearest well from Avhich water is 

 drawn to the one in which the gauge is established is on tlie east side, 

 about 60 yai'ds distant. 



In the following table the dates refer to the interval between noon of 

 one day to noon of the succeeding day. The figures in the columns 

 indicate the hours at which the well commenced to sink and then to rise 

 in the afternoon and evening, and when it again commenced to sink and 

 to rise in the morning. The time midway betM^een the rising in the 

 evening and the sinking in the morning may be taken as the crest of the 

 night wave, the crest of the midday wave being halfway between the 

 A.M. rising and the p.m. sinking of the next day. The omission of dates 

 or hours indicates that the inflections on the diagram were indistinct or 

 absent. The letters R, F, or S in the sixth column indicate whether the 

 well was rising, falling, or steady. 



The time at which the well commences to rise in the evening is 

 fairly constant, about 8 p.m. This precludes the idea that the diurnal 

 motion may be dependent upon the tides in the neighbouring bay, 

 which is some two miles distant. The most irregular figures are those 

 indicating the time at which the well commences to sink in the morning, 

 which as summer approaches, when the city rises at an earlier hour, also 

 tends to become earlier, and therefore assist in confirming the suggestion, 

 that the rising and falling of the water are due to the facts that larger 

 quantities of water are being used in the morning and evening than are 

 being used during the middle of the day and the middle of the niglit. 



The amount of these fluctuations has seldom exceeded 5 mm., and 

 the day and night waves have about the same amplitudes. Professor 

 Franklin H. King found that a heavily loaded train moving slowly 

 past a well at a distance of 140 feet caused the water in the well 

 to slightly rise, from which it might be inferred that the rising and falling^ 

 of water in a well might be accompanied by a rising and sinking of the 

 surrounding sui'face. If this were the case then during a day and night 

 the horizontal pendulums in Tokio ought to show a double curve. In 

 some few instances there is a tendency to show such a double motion, as, 

 for example, in fig. 5, Plate II. But because one of the curves is faint 

 and because it is of rare occurrence, the 12-hour movement in the well is 

 by no means sufficient to explain the daily wave indicated by the pendulums. 

 It must, however, be reiuarked that the period of well observations coin- 

 cides with a period when daily curves were not well marked, and what 

 happened in the well when they were distinctly marked I have at present 

 no means of ascertaining. 



