THE TIDES. 159 



surface of the earth, and which was not the 

 primary object of their investigation is in some 

 respects more interesting than what they sought 

 and did not find. The delicate investigation thus 

 opened up promises a rich harvest of knowledge. 

 These disturbances are connected with earthquakes 

 such as have been observed in a very scientific 

 and accurate manner by Milne, Thomas Gray, 

 and Ewing in Japan, and in Italy by many 

 accurate observers. All such observations agree 

 in showing continual tremor and palpitation of 

 the earth in every pnrt. 



One other phenomenon that I may just refer 

 to now as coming out from tide-guage observa- 

 tions, is a phenomenon called seiches by Forel, 

 and described by him as having been observed 

 in the lakes of Geneva and Constance. He 

 attributes them to differences of barometric 

 pressure at the ends of the lake, and it is pro- 

 bable that part of the phenomenon is due to 

 such differences. I think it is certain, however, 

 that the whole is not due to such differences. 

 The Portland tide curve and those of many other 



