546 
THE GEOLOGIST. 
unequal contractions of its different parts; and in a cooling globe compound 
gases could not be expected to produce any decided meclianical effect, at least 
without materially altermg tlie composition of the atmosphere. But, apart 
from these causes, the trausitiou of the igneous rocks from a fluid to a solid 
state would be attended with occasional paroxysmal movement and change. 
Being dependent on hydrostatic conditions for stability, the different parts of 
the earth's crust must extend into the greater reservoir of lava to a depth in 
some measui'c proportionate to the elevation above its sui-face. Continents 
must rest on solid foundations far deeper than those which supported the body 
of the ocean ; and the violence which subterranean forces manifested in several 
islands might be ascribed in part to the weakness of the barriers which re- 
strained them. Inequalities in the solid envelope of our globe were indicated 
with some certainty by local forces of gravity. The anomalous character of 
the vibrations of the pendulum, when applied in some places, justified the con- 
clusion that the invisible side of the earth's crust contained the greatest 
irregularities, and that our continental tracts of land rest on the bases of 
gigantic subterranean mountains, whose tops might be depressed even three 
or four hundred miles below the mean level of the solidified matter. The 
accumulations of solid matter on the internal mountains must ultimately be 
crushed by the strain which their augmented size occasioned ; a mighty 
avalanche of rock would then tumble to the thinner pai-t of the earth's crust. 
Regarding these masses as the cause of earthquakes, they might account for 
the instantaneous manner in which shocks of earthquakes occurred, their 
extreme violence, and destructive character near the coasts of continents and 
on adjacent islands, while they were almost imperceptible in the interior of 
continents. It was probable that the ascending movements of silica, and 
perhaps of other isolated matter, might serve to bring the heavy metallic 
deposits from the central to the superficial regions of our planet; and tlie 
general occurrence of gohl in auriferous quartz-rock might thus admit of 
plausible explanation. 
THE FORMATION OF LAND. 
By the Eev. C. R. Gordon, M.A., F.R.S. 
The Bev. C. B. Gordon, M.A., F.R.S., proceeded to say that the solid parts 
of the globe are in general composed of sand, gravel, argillaceous and cal- 
careous strata, or of the various compositions of these with other substances. 
Calcareous bodies belong to the sea, and are formed in it. There are only two 
ways by which porous or spongy bodies can be consolidated, either by conge- 
lation or attrition. To procure solidity, it must be brought about by inducing 
fluidity, either immediately by the action of heat, or directly by the operation 
of a solution. Thus, fire and water maybe considered as the general agents in 
this operation. The strata formed at the bottom of the sea are to be con- 
sidered, therefore, as having been consolidated either by aqueous solution and 
crystaUizatiou, or by the effect of heat and fusion. Vi e have strata consolidated 
by calcareous spar. We have strata made solid by fluor, a substance not 
soluble, so far as is known, by water. We have strata consolidated with sul- 
phureous and bituminous substances, which do not correspond to the solution 
by water. We have strata consolidated with siliceous matter, in a state totally 
different from that under which it has been observed, on certain occasions, to 
be deposited by water, some consolidated by felspar, a substance indissoluble 
in water, some also consolidated by almost all the various metallic substances. 
