132 REPORT— 1895. 



its existence in such places, and had instruments of greater sensibility been 

 employed it is likely that it might have been detected. It was perceptible 

 and often measurable, but by no means pronounced in the records from 

 my house (A), where the instrument was well founded and in an east and 

 a west direction, well protected from temperature effects upon the sur- 

 rounding soil. It must not be forgotten that this instrument was the 

 most sensitive, being capable of recording changes of 0"-l. Had the 

 sen.sibility of this instrument not exceeded that of other instruments less 

 favourably installed, it is doubtful whether it would have shown any 

 marked trace of the daily wave. 



Two instruments in an underground chamber (E and F), where as in the 

 caves the daily change in temperature did not exceed P C., often showed 

 the daily wave in a marked manner, but it was not so great as it was at 

 stations J and Iv upon the surface. The conclusion to which these 

 observations lead is that the daily wave is not due to fluctuations in tem- 

 perature immediately near to the instruments, but that it is a surface 

 phenomenon which penetrates to a depth of at least 12 feet in the 

 alluvium. 



An instrument upon the surface (J) the ground round which was 

 exposed to the sun upon all sides excepting the east, and another (K) 

 which was exposed on all sides excepting the west, showed large diurnal 

 waves, and notwithstanding the fact that between these two stations there 

 was a pond and a grove of tall trees, the pendulums usually moved in the 

 .same direction at about the same time. The magnitude of the movements 

 was different, but with this exception the only other difference was that 

 J, the open ground round which was exposed to the afternoon .sun for one 

 or two hours longer than the open ground round K, continued its westerly 

 motion for one or two houi-s longer than K (figs. 7 and 8). 



An experiment made at J was to dig a trench 5 feet in depth round 

 the south and west sides of the hut. This did not appear in any 

 way to affect the amplitude of the daily wave, but it seemed to increase 

 the suddenness with which the westerly displacement commenced, and at 

 the same time the number of hours occupied in making a complete wave 

 was reduced. With an instrument at O, a few yards from J, which 

 recorded north and south motions, the wave was regular but of small 

 amplitude, the northern movement coinciding with the western motion of 

 J and K. The direction of maximum tilting may therefore have approxi- 

 mately l)een W.N.W. and E.S.E. On the western side of a plateau 

 facing the eastern slope of the plateau on which A, J, K, and O were 

 situated, an instrument N showed a daily wave, but the xoesterly exciorsion 

 of ihe pendulum loas completed only a feio hours later than the easterly 

 excursion was completed by those iipon the opposite hill. It appeared as 

 if the two bluffs, or at least the trees upon them, inclined towards each 

 other, and then away from each other once in twenty-four hours. 

 Between the two bluffs there is an open valley, in which there'is a lake or 

 pond nearly half a mile in breadth. 



That the records at N were small may be attributed partly to the fact 

 that the instrument never had given to it any great degree of sensitive- 

 ness, and partly to the fact that on all sides excepting the west the ground 

 immediately round the instrument was well shaded by tall trees. There 

 is, however, a large open space about 100 yards to the east of this station. 

 At another station P, on the eastern side of the plateau, on which N was 

 situated, and at a distance fz-om it of about 200 yards, the movements, 



