160 Alternating Currents. [April, 
immediately rose about eight feet.” Those ‘‘ mountainous” 
waves, therefore, which overwhelmed the Peruvian cities of 
Iquique and Arica, on the 13th of August, 1868, were 
nothing more than might have been anticipated from the 
illustration by the harp-string and pendulum. For the 
great wave, forty feet high, which completed the destruction 
of Iquique (directly after the earthquake shock had laid it 
in ruins) was immediately preceded by a retirement of the 
sea to the extraordinary depth of four fathoms. It was 
by a still higher wave, arising from an apparently still 
greater retirement of the sea, that Arica was destroyed, 
as appears from the following account given by Mr. 
Nugent, H.M. Vice Consul, in the ‘* South American 
Missionary Magazine” for October, 1868. ‘In the after- 
noon of August 13, 1868, about 5 o’clock, we were visited 
with a most tremendous earthquake. I had _ scarcely 
time to get my wife and children into the street, when the 
whole of the walls of my house fell, or rather were blown 
out, as if jerked at us. I started over the trembling ground 
forthé hills. . . . A great crywent upto heaven, suchas 
few’men have heard, ‘The sea is retiring.” . . I looked 
back. . . . Isaw all the vessels in the bay carried out 
irresistibly to sea (anchors and chains were as packthread), 
probably with aspeed of ten milesan hour. Ina few minutes 
the great outward current stopped, stemmed by a mighty rising 
wave, I should judge about fifty feet high, which came on with 
an awful rush, bringing in the whole of the shipping with it, 
sometimes turning in circles as if striving to elude their 
PARES oo tst The wave passed on, struck the mole into 
atoms, swallowed up the Custom-House, . . . carried 
everything before it. Ina few minutes all was completed— 
every vessel was either ashore or bottom upwards.”  ‘‘ The 
mighty rising wave” here described was evidently the 
accumulation produced by “‘ the great outward current,” and 
that outward current was caused by “ the trembling ground” 
beneath the sea, that is by the rapid vibrations of the 
inclined bed of the sea descending from the shore; for as ~ 
the dry land was then “ ivembling” or vibrating by the 
vertical shock, the adjoining submarine ground must have 
been so also. This is a fair specimen (aithough on a terribly 
large scale) of all those extraordinary agitations now under 
consideration. 
Mr. Mallet, however, entertains the idea proposed by 
Michell a century ago, that these extraordinary influxes 
proceed from the offing, and from vast but very low waves 
formed by submarine earthquakes or volcanos at the distance 
"ead 
