192 USVRAIGIL, (Co IOS SVAILIL 
tal, that pressure brought to bear on the plastic interior—either 
by reason of the cooling and contraction of the earth’s crust, or 
by the shifting of material on the surface, in the constantly active 
processes of denudation, transportation and sedimentation — 
would most reasonably be expected to cause the rocks to bulge 
upward into domes. 
If the above considerations are well founded we should expect 
to find subtuberant uplifts in the central portions of continental 
areas, but not about their borders. Here, again, it would be well 
to check inference by observation, but so far as I am aware, 
mountains of the type referred to, have not been recognized out- 
side of the United States. Although unable to verify our conclu- 
sion, at present, we can leave it as a prediction, the truth or 
fallacy of which will appear as exploration is continued. 
Analogies between subterranean and surface igneous phenomena.— 
Certain analogies between the phenomena associated with subter- 
ranean intrusions and with surface extrusions or volcanoes, are 
of interest. 
Quiet eruptions of highly liquid basaltic lava, like those 
characteristic of the Hawaiian volcanoes, are represented below 
the surface by widely extended intrusive sheets of similar material. 
The thick and sluggish volcanic flows of rhyolite of the character 
to be seen on the side of the Mono craters, California, are sug- 
gested by the cistern-like intrusions of refractory porphyrite, 
forming laccolites, and still more strongly by plutonic plugs in 
which no lateral expansion has been recognized. Fissure erup- 
tions, like those that furnished the Columbia lava of Idaho, 
Washington and Oregon, or the Deccan traps of India, so far as 
the energy manifest, and the extent of topographic changes pro- 
duced, are concerned, find more than a counterpart in subtuberant 
mountains. 
Extremely violent volcanic explosions occur when large 
bodies of water come in contact with molten lava. A molten 
magma rising from a deeply seated source in the earth’s crust, 
as a rule, invades strata that are more and more highly water- 
charged, the nearer it approaches the surface. A secondary 
