770 On the Evidence that the Earth’s Interior is Solid. (August, 
places and elevated in others. The depression of any portionof — 
the crust into the viscous liquid beneath would cause the eleva 
tion of an equivalent weight of the liquid material; as in the case 
of ice, the depression of the ice on one side causes the heavier 
water to overflow unless it can escape in some other direction. a 
The simple sinking of a portion of the crust on one side with its 
corresponding but less elevation on the other, with the attendant 
fissuring, affords all the dynamic agent needed to raise lavas to 
the top of the highest mountains ;! while if in any way the yield 
ing to the lateral compression should be sudden, instead of grad 
ual, owing to fracturing and slipping of the parts, an earthquake 
shock would result. 
If the general views of the compression of the material-in the 
interior of the earth are correct, then if from any cause the pres- 
sure were removed, the natural expansion of the material, if a 
liquid, would cause it to rise to some extent in any vent oF 
opening. 
During the earlier times when the crust was thinner and the 
internal heat stronger, a greater variety and amount of mat 1 
raised as lavas through the fissures would be expected, and not 
improbably outflows of two different kinds might take place : 
at the same time, as it would seem had taken place on Lake 4 
Superior. : 
The up thrust of the still liquid and yielding interior portions 
through the fissures in the overlying crust, and the subsequent 4 
solidification of the intruded material, would cause that crust to 
be tied through and through with the underlying mass. abe 
Neither is it to be expected that the contraction woul ie 
equal in every portion, while the depression of the ere 
the interior would give rise to unequal thicknesses of as as 7 
to which the liquid outfows would add. The great irreg® l 
of the under surface of thè crust, coupled with th d 
sage from the solid to the viscous liquid interior would pae “ 
to prevent any of the supposed slipping of the crust a a 
interior, as many physicists have assumed would take place 1! = 
earth had a liquid interior. 
If it is held that volcanic rocks are derived fro q 
faction of the original crust of the earth, would gee! oe ] 
theory be, in the light of what is now known of the 
? Whitney, “ Earthquakes, Volcanoes and Mountain-building,” P- * 
