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to be rife during the consolidation of a cooling planet. But 
the evidence which was believed to support this theory of the 
development of our planet breaks down on a calm investiga- 
tion of facts. We ignore the volcanic forces that still exist ! 
What lakes or sea of lava must underlie the volcanic districts 
of the Andes and Indian Archipelago at the present moment, 
and what masses of molten matter, which never appears at 
the surface, must be injected every year, in earthquake dis- 
tricts, into rock fissures, or into the beds of the different seas. 
Yolanic action, with its evidence of the earthquake, and great 
outpourings of traps, lavas, and other materials, has left its 
undoubted marks throughout the Cambrian, Silurian, Carboni- 
ferous, and every other geological period; but the Plutonic 
masses that have been erupted from the interior of the earth, 
and the earthquake movements which are known to have 
occurred since the commencement of the Tertiary periods, have 
been enormous, and may well cause us to pause ere we assign 
to any geological period in particular the peculiarity of an 
“ earthquake age.” 
I have made the preceding remarks upon direct volcanic 
action, because intensity of earthquake action appears to be 
connected with volcanos and their effects. Indeed, Mr. 
Mallet, who is the highest authority upon the subject, believes 
that (c an earthquake, in a non- volcanic region, may be viewed 
as an uncompleted effort to establish a volcano.” Questions 
have arisen as to whether all earthquakes are produced by 
volcanic action, and an ingenious problem has been broached 
by Mr. Mackie, the editor of “ The Geologist,” in the No- 
vember number of that periodical, as to “ whether some earth- 
quakes may not be due to the crystallization of rock masses 
under the pressure of superincumbent strata, and that they 
are f the shocks 3 of the rupture of masses of dense strata, 
or the sudden slippings of one great rock formation over 
another.” This theory of Mr. Mackie' s brought forth a letter 
from Mr. Scrope, which is published in the December number of 
“ The Geologist,” who refers earthquakes of all kinds to the 
same primary cause as the volcanic eruption ; and thinks it 
quite “ unnecessary to resort to any other, such as terrestrial 
electricity, magnetism, crystallization, the breaking in of the 
roofs of imaginary subterranean cavities, or the condensation 
of vapour evolved from submarine volcanoes.” In this sup- 
position I entirely agree with Mr. Scope, and believe that it is 
altogether unnecessary to resort to imaginary hypotheses to 
explain those phenomena which are accounted for by so many 
examples and recorded facts. I do not conceive that we 
have any evidence whatever to suppose that “ snaps, and 
jars,” or earthquakes of any kind, are independent of volcanic 
