328 EARTHQUAKES. 



these tips of the soil take place — which phenomena are 

 noticeable in seismic as well as microseismic motions — 

 Rossi states are related to the direction of certain lines 

 of faulting. 



Indications of levels, — Bubbles of delicate levels 

 can be easily seen to change their position with meteoro- 

 logical variations ; but Rossi also tells us that they change 

 their position, sometimes not to return for a long time, 

 during a microseismic storm. Here again we have another 

 phenomenon pointing to the fact that microseismic dis- 

 turbances are the companions of slow alterations in 

 level. 



One of the most patient observers of levels has been 

 M. Plantamour, who commenced his observations in 1878, 

 at Secheron, on the Lake of Geneva. He used two levels, 

 one placed north and south, and the other east and west. 

 During the summer of 1878 the east end rose, but at 

 the end of September a depression set in. The diurnal 

 movements had their maximum and minimum at 6 and 

 7.45 A.M. and p.m. The total amplitude was 4*89'^ 

 The variations of the east and west level appeared to 

 be due to the temperature, but the movements of the 

 north and south level were dependent upon an unknown 

 cause. 



Between October 1, 1879, and September 30, 1880, 

 the east end fell rapidly, from the middle of November 

 up to December 2Q, amounting to 88*71''. It then rose 

 Q'Qb" to January 5, and then fell again. On January 28 

 it reached 89*95'', after which it rose. 



Between October 4, 1879, and January 28, 1880, 

 the movement was 95*8", against 28*08" of the previous 

 year. 



These movements were not due alone to temperature. 

 The north and south level, which was not influenced by 



