66 Mr. Matter on the Dynamics of Earthquakes. 
«“ During most great earthquakes, and especially in those on the west coast of 
America, it is certain that the first great movement of the waters has been a 
retirement. Some authors have attempted to explain this by assuming that the 
water retains its level while the land oscillates upwards; but surely the waters 
close to the land, even of a rather steep coast, would partake of the motion 
of the bottom. Moreover, as urged by Mr. Lyell, similar movements of the 
sea have occurred at islands far distant from the chief line of disturbance, 
as was the case with Juan Fernandez during this (Conception) earthquake, 
and with Madeira during the famous Lisbon shock. I suspect,” he says “ (but 
the subject is a very obscure one), that a wave, however produced, first draws 
the water from the shore, on which it is advancing to break. It is remark- 
able that while Talcahuano and Callao (near Lima), both situated at the head 
of large shallow bays, have suffered severely during every earthquake from 
great waves, Valparaiso, seated close to the edge of profoundly deep water, has 
never been overwhelmed, though so often shaken by the severest shocks. From 
the great wave not immediately following the earthquake, but sometimes even 
after the interval of half an hour, and from distant islands being affected simi- 
larly with the coast, near tbe focus of the disturbance, it appears that the wave 
first rises in the offing, and as this is of general occurrence, the cause must be 
general: I suspect we must look to the line where the less disturbed waters of 
the deep ocean join the water nearer the coast which has partaken of the move- 
ment of the land, as the place where the great wave is first generated. It would 
also appear that the wave is larger or smaller according to the extent of shoal 
water that has been agitated, together with the bottom on which it rested.” _ 
Darwin fails in giving any explanation of the phenomena, in fact he does not 
pretend to offer any. 
Michell, upon this point (and it is one of the most important and fruitful 
facts in the whole range of earthquake phenomena) is totally astray ; he attributes 
the retreat of the water from the shore, previous to the advance of the great 
wave, to a distant subsidence somewhere in the bottom of the sea, from the sudden 
giving way of some cavity, in consequence of a vacuum produced by the conden- 
sation of steam; or he supposes that the whole mass of the land may be suddenly 
elevated by pent-up steam beneath it, and let down again upon its escape, and 
