DISTURBANCES IN THE OCEAN. 177 



These sudden alterations in the levels of coast lines 

 have already been referred to. 



Other points which are difficult to understand are the 

 occurrence of disturbances in the sea at the time of feeble 

 earthquakes, and with earthquakes occurring in distant 

 places. As examples of such occurrences, Fuchs quotes 

 the following : ' On May 16, 1850, at 4.28 a.m., an earth- 

 quake took place in Pesth, and at 7.30 a motion was 

 observed in the sea at Livorno. Again, at the time of the 

 earthquake of December 19, 1850, which shook Heliopolis, 

 a flood suddenly came in upon Cherbourg.' May not these 

 phenomena be the result of an earth pulsation, which 

 produced an earthquake at one point, and a sea wave at 

 another ? 



Equally difficult to understand are the observations 

 when the disturbance in the sea has occurred several 

 hours after an earthquake ; as, for instance, at Batavia, in 

 1852, when there was an interval of two hours; and to 

 this must be added the observations where the motion of 

 the sea has preceded that of the earthquake — as, for in- 

 stance, in 1852, at Smyrna. Whilst recognising the fact 

 that it is possible to suggest explanations for many of 

 these anomalies, we must also bear in mind that they are, 

 generally speaking, exceptional, and, in some instances, 

 may possibly be due to errors in observations. 



Velocity of propagation of sea waves, amd depth 

 of the ocean, — It has long been known to physical science 

 that the velocity with which a given wave is propagated 

 along a trough of uniform depth, holds a relation to the 

 depth of the trough. 



If V is the velocity of the wave, and h the depth of 

 the trough, this relation may be expressed as follows : — 



A = — or ^ 



=(iy 



