130 



REPORT — 1895. 



taken place may be due to the direction in which the instruments or their 

 foundations have wai'ped, or, what is equally probable, they may each 

 have moved away from an exposed area which, in consequence of evapora- 

 tion, may have been rising. About this general movement of the pendulums 

 which might be included in the previous section of this report, because it 

 only refers to observations extending over fifty-two days with pendulum*, 

 one of which had a light foundation, no definite conclusions can be stated. 



One thing, however, which is clear, and which can hardly be 

 attributed to" the warping of instruments or their foundations, is that 

 the pendulums Avandered at the same time in the same directions. For 

 the first four days the pendulums at A and J moved westwards, for the 

 next twelve days they moved eastwards, after which there was a slight 

 westerly and then an easterly motion up to the fortieth day, when they 

 both turned quickly westwards. This synchronism in direction of motion 

 is evidently due to some general cause, which may act on the surface of 

 the earth or within its interior. A barometric curve determined in 

 a manner similar to that in which the curves for A and J were deter- 

 mined shows that atmospheric pressure was near its maximum when the 

 pendulums were at their western limits, but the relationship between this 

 curve and those of the pendulums is not sufficiently clear to conclude 

 that the movements of the pendulums have been altogether due to 

 fluctuation in atmospheric pressure. Possibly the movements may have 

 been due to evaporation and precipitation lightening or loading some 

 particular area in the vicinity of the pendulums. 



The earthijuakes of local origin indicated by circles on the curve for 

 A, which occurred during the time that there was a rapid westerly 

 motion, suggest the idea that the movements may have a hypogenic 



(/) On the daily change in the jwsition of the pendulums. 



The table below gives in millimetres the difference in the mid-day read- 

 ings of the positions of the pendulums A and J. The sign -f- indicates- 

 that during the past twenty-four hours the pendulum has moved so many 

 millimetres towards the west, while the sign — indicates a displacement 

 towards the east. The sign ? means that no reading had been taken or 

 that no displacement was observed. 



