Mr. Mautet on the Dynamics of Earthquakes. 73 
The streams, whose beds were in the bottoms of the valleys, now quickly 
formed lakes above these dams, and their final overflow often traced out new 
river courses over the table land, or changed the whole aspect of the valleys 
below by violent «‘debacles” consequent upon their giving way. I notice these, 
and refer to Dolomieu’s Dissertation for many other singular details, in order to 
remark that those and all similar phenomena do not properly constitute part of the 
earthquake at all; and, in order to form clear notions of earthquake mechanics, we 
must carefully distinguish between these, which are but consequences of the con- 
sequences of the earthquake, and the earthquake wave itself, which gives rise to 
them all. The earth wave shakes the country ; the features of its surface are altered 
by the filling of valleys and levelling of eminences ; a new state of things is in- 
stantly brought about, as regards its drainage, and all its meteorological circum- 
stances alter in proportion. Hence, when, in the loose narratives of earthquakes, 
which abound with ill-made observations, fanciful and figurative language, and exag- 
geration, we read of ‘lakes suddenly appearing where all was dry before,” rivers 
and lakes “bursting up out of the earth,” “lightnings and clouds of smoke 
or dust accompanying the shock,” we must bear in mind that these are mere 
accidents, contingent upon the consequences of the principal phenomenon, the 
transit of the earth wave, namely, upon the disturbance of the surface of the land 
reacting upon its drainage, and producing violent electrical disturbances by fric- 
tion, by pressure, by changes of temperature, and these all again reacting upon its 
climate, so as often permanently to affect it. 
Hence, to arrive at a true theory of earthquake mechanics, it is not required 
that we should be able to predict, or even to explain, all of these dowbly secondary 
contingent circumstances, the conditions of which must be, for the most part, so 
local as to forbid the attempt. Many, however, of such contingent phenomena, 
where we have the conditions sufficiently given, can be explained by direct refe- 
rence to our theory. 
For instance, Dolomieu records of Calabria, and the same statement is 
made of other earthquakes, that, “at the moment of the shock, several springs 
spouted up their water like fountains.” The sources of copious springs usually 
lie in flat plates or fissures filled with water, whether issuing from solid rock, or 
from loose materials: now, if a vein, or thin, flat cavity, filled with water, be in 
such a position that the plane of the plate of water or fissure be transverse to 
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