On Earthquakes. 195 



ocean, and diminution over corresponding portions of the land, we are not at 

 a loss to perceive how the elastic power of subterranean fires, thus repressed 

 on the one hand and relieved on the other, may break forth in points when 

 the resistance is barely adequate to their retention, and thus bring the 

 phenomena of even volcanic activity under the general law of solar 

 influence." 



The remarks in the above quotation concerning the " transfer of 

 matter," appears to us to be of great importance in treating upon the causes 

 of earthquakes. All the great formations of rock of a secondary origin 

 consist of matter which does not occupy at present its original position upon 

 the surface of the earth. Tiie sedimentary rocks of North America are, in 

 Pennsylvania, about four miles and a half in thickness, or in other words 

 that part of the earth's surface is covered with a sheet of solid rock four and 

 a half miles thick, the material of which has been transported from some 

 other place. The effects of this enormous " transfer of matter" should have 

 been the same as if the continent of North America were to be taken up 

 bodily to the depth of four and a half miles and laid down upon the surface 

 of Europe. If it be true, as many geologists suppose that the interior of the 

 earth is in a semi-fluid state, it is probable that the addition of this enormous 

 load of rock to the surface of Europe would cause the crust to sink down in 

 that part of the world and force the subjacent fluid matter away under other 

 regions, which would be elevated in consequence. The effects would be no 

 doubt felt all over the world. New countries would rise up out of the sea, 

 volcanoes would burst forth and all the present arrangements of land and 

 water upon the face of the globe be changed. The consequences would be 

 nearly the same, were the transfer to be made gi'adually instead of all at one 

 time. Were one foot in thickness of rock only to be laid upon the surface 

 of Europe in a thousand years, and were the process of accummulation to • 

 continue for a sufficiently great period of time, the burden would in the end 

 become too great to be sustained, and a sinking of the surface must take 

 place. The effects, instead of occurring all at once in one grand and general 

 convulsion affecting the whole earth's surface, would be distributed piecemeal 

 throughout many ages, and save, by a slight shudder now and then,, indicat- 

 ing that some stratum of rock far beneath the surface had given way, would 

 be imperceptible. Still, although the process might be slow yet it would be 

 sufficient to occasion all the earthquakes, volcanoes, elevations and subsi- 

 dences of land that have been noticed in historic times, or which can be shewn 

 to have taken place in former ages. 



The suggestion of Sir John Herschel, however, would only explain the 

 phenomena of earthquakes, were it true that the interior of the earth is in a 

 fluid state. Many facts, such as the increase of heat in deep mines, the rising 

 and sinking of land, and the molten overflowings of volcanoes, seem to 

 demonstrate that such is the condition of the interior ; but, on the other 

 hand, some of the most eminent mathematicians have carried through certain 

 calculations of great complexity which appear to prove that either it is solid 

 throughout, or that the crust is of such great thickness and strength that the 

 transfer of very considerable masses of matter upon the surface would procdue 

 little effect. We shall probably in a future article give some account of tasoq 

 calculations. 



