Mr. Mauer on the Dynamics of Earthquakes. 99 
great general region of local sudden elevation, within which we are to look most 
commonly for the earthquake’s origin, exists as a broad belt surrounding the land; 
within this belt all the diversified deposits of the detritus of the land are con- 
stantly taking place, shifted and modified subsequently by tidal currents, &c. ; 
hence, within this space the isogeothermal planes are in a constant state of fluc- 
tuation, now rising, where a thick coat of badly conducting matter is locally 
deposited, and again rapidly sinking as it is swept away. Such a condition of 
the sea bottom would seem to be the most likely state of things to give rise to 
frequent and sudden local elevations, or even submarine eruptions of molten 
matter, as has been well explained by Herschell and Babbage. 
Since writing the preceding pages, and not before, I have been enabled 
to read the portions of Humboldt’s Cosmos which treats of earthquakes. On 
opening this book I fully expected to have found my views anticipated by the 
great German philosopher. In this, however, I find I was mistaken. While 
admiring the exuberance of facts, the copious sources of far-drawn observation 
of the veteran traveller, I was disappointed to find that Humboldt had not even 
made the attempt to frame a theory of earthquake motion. He notices the 
transit of the shock as of waves of some sort (as many others have done before ), 
and even suggests their production at centres of disturbance, and hints at their 
having some connexion with the elasticity of the rock through which they pass, 
and at their possible mutual intersection and interference; but it is impossible to 
discover (throughout the whole chapter) that he has formed any distinct idea as to 
the nature or mode of propagation of the great earth wave. At one place the 
reader is led to fancy that he speaks of the wave of elastic compression in the 
solid crust, which I contend to be the true earthquake wave ; but again, in finally 
summing up his views, he seems completely to adopt those of Michell. He 
says, “the filling up of fissures with crystalline matter interferes by degrees 
with the free escape of vapours, which, confined, become operative through their 
tension in three ways, concussively, explosively, or suddenly up and down, and, 
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