80 Mr. Matter on the Dynamics of Earthquakes. 
Lyell’s explanation of the alternate opening and closing of fissures, namely, 
that “we must suppose the earth was by turns heaved up, and then let fall 
again,’* seems erroneous and unsupported by observation; no amount of ele- 
vation, transitory or permanent, recorded in even the most violent earthquakes, 
would be sufficient to account, in this way, for the opening and closing of 
fissures of a few inches in width, much less of several feet, as repeatedly observed. 
As it has been before remarked, that the cotidal lines of the earth wave 
become distorted by passing through heterogeneous masses, so, in passing 
through a broken country of variable formation, two partial earth waves, separated 
from the original wave, may cross each other, and produce a larger wave at this 
nodal point, and in this case we shall have fissures, also intersecting or radiating 
in various directions from the centre of the node, like cracks in a broken pane of 
glass, which is the explanation I would give of this phenomenon, as observed in 
the great Calabrian earthquake of 1783, at Jerocarne.f It is exceedingly impro- 
bable that radiating fissures, so produced, should ever all close again after the 
transit of the wave, as many of the cuneiform masses between them must become 
greatly displaced; their remaining open partially is, therefore, no proof of per- 
manent elevation, as Mr. Lyell supposes. 
On the other hand, it may occur that the earth wave, in passing from 
heterogeneous formations of low elasticity, into one vast and deep homogeneous 
formation, as, for instance, of crystallized igneous rocks, possessing a high elas- 
ticity, will be largely increased in amplitude, and thus may (like the great 
sea wave over the deep ocean) pass through such a country, with its immense 
velocity unabated, and yet, from its small altitude, and great amplitude, or, in 
other words, from the great breadth and flatness of the wave, it may do no mis- 
chief, nor even be noticed, except in the slight agitation it may produce in lakes 
or other inland waters. 
This appears to have been the fact with the great Lisbon shock, on reaching 
the crystallized primary or igneous rocks of Scotland, where its passage was only 
known by the disturbance of the waters of the Highland lakes. 
At Loch Lomond the water, without any apparent cause, rose against its 
banks, and then subsided below its usual level: the greatest height of the swell 
* Lyell, vol. i. p. 483, + Ibid. p. 507. 
