68 Mr. Mattet on the Dynamics of Earthquakes. 
bed of the deep ocean; let it be a submarine eruption of actual lava poured out, 
a sudden breaking through of the earth’s crust and injection below with lava, or 
any other disturbance, it matters not what, sufficiently sudden, violent, and ex- 
tensive to produce an earthquake. The impulse at this centre will spread itself 
in all directions, but for simplicity we will limit our consideration to what will take 
place as respects a single distant land within range of the earthquake. 
The original impulse given to the bed of the sea acts simultaneously upon the 
earth, the sea, and the atmosphere, originating at the same instant, and transmit- 
ting one or more waves through each. 
The earth wave moves with an immense velocity, probably not less than 
10,000 feet per second, in hard stratified rock, and perhaps little short of this in 
the less dense strata. 
Dolomieu says of the Calabrian shocks: “ They were as sudden as the blow- 
ing up of a mine.” 
It will be proper here to give some proof of the actual progressive motion 
of the earth wave or shock; that each portion of the disturbed country is 
shaken in succession by the progress of the earth wave, and not the whole 
at once, as very commonly believed. Thus Spallanzani, in his Travels in 
the two Sicilies, in recording the facts observed by him of the earthquake at 
Messina (part of the great Calabrian earthquake), says: “ A very violent noise, 
like the rolling of carriages, was first heard at Messina, while a thick cloud (of 
dust) rose from the shore of Calabria opposite, where was the centre of the 
earthquake, the propagation of which was apparent by the successive falls of 
buildings from the point of the Faro to the city of Messina, as if, at the former 
point, a mine had been sprung, which extended along the shore, and continued 
into the city.” 
It is needless to multiply such facts, which occur abundantly in earthquake 
narratives, to prove that the earth wave passes parallel to itself in succession 
through the shaken country. I shall shew hereafter, however, in speaking of 
systems of vibrations, that, under particular conditions as to geological formation, 
the whole mass of a country may be shaken at one and the same instant. 
The earth wave, or shock, reaches the devoted land at the same instant that the 
sound of the crash and thunder of the submarine war of elements reaches the ears 
of its inhabitants, for the wave is itself the bearer of the sounds first transmitted 
