390 SEE— THE CAUSE OF EARTHQUAKES. LOctober 19, 



be explained except by explosions in the earth. Some of the land 

 was no doubt simply settled by shaking, but this will not account for 

 the upheaval of the bed of the Mississippi River so as to make its 

 waters flow upstream ; and we seem obliged to admit that in addition 

 to subsidence there was also elevation of ground. 



The New Madrid earthquake is extremely remarkable for its nu- 

 merous severe shocks and the long intervals at which they occurred, 

 the last great shock of February 7, 181 2, being the worst of all. The 

 order of events does not harmonize so well in the tectonic theory of 

 rock slipping as it does with Strabo's account of a volcanic out- 

 break near Chalcis, in Euboea, in which the shocks ceased only 

 after a fissure opened on the Lelantine Plain and ejected a fiery 

 river of mud. To be sure, no lava was ejected in the New Madrid 

 earthquake, but the phenomena resemble those described by Strabo, 

 in which elastic vapors within the earth were seeking release. If 

 no single outburst of lava and steam could break forth above ground 

 the agitation might on that account continue all the longer, and an 

 impartial study of this remarkable earthquake strongly suggests 

 this explanation. The whole course of events is singularly incon- 

 sistent with any suggestion that mere slipping of rock or subsidence 

 was involved. 



We have examined this earthquake in detail, because it is little 

 understood and so complex and extraordinary in respect to location 

 and duration that it constitutes a severe test of any theory ; and yet 

 a comprehensive theory must be able to account for such phenomena 

 without prejudice to the historical facts. 



§ 53- Other important earthquakes. 



If we examine attentively the available details of various other 

 earthquakes which are classed as tectonic we shall find that most 

 if not all of them give evidence of high explosive power within 

 the earth. Under ordinary conditions it may be supposed that these 

 forces are exerted long enough to afford partial or complete release 

 from the strain, and then the agitation ceases or continues in the 

 form of slight after-shocks. It is only when unlifts occur that 

 we have direct proof of an uplifting force, the visible effect of 

 subterranean explosive power; but it would seem that the heaving 

 of the earth accompanying the rending of strata and breaking of 



