Association of American Geologists and Naturalists. 275 



constitutes, as my brother and myself have endeavored to show, an es- 

 sential feature in all movements of elevation. Regarding such disturb- 

 ances as a true billowy pulsation of the flexible crust of the globe, we 

 have deduced from data connected with some of the best authenticated 

 earthquakes, the extraordinary progressive velocityof the undulations of 

 the ground, and have shown that when the pulsation has been imparted 

 to the sea, the vast waves engendered have moved at the amazing speed 

 of one mile or more per minute. Making every abatement for resist- 

 ance from the comparative shallowness of a continental inundation, the 

 phenomena of earthquakes fully justify us in the belief that the broad 

 and rapid onward undulations of the ground would be propagated to an 

 uplifted sea above, and the gigantic billows be propelled across the sur- 

 face of the heaving land, with a velocity and a propulsive energy ap- 

 proached by no other possible terrestrial current. 



If we will conceive, then, a wide expanse of waters, less perhaps than 

 one thousand feet in depth, dislodged from some high northern or cir- 

 cumpolar basin, by a general lifting of that region of perhaps a few 

 hundred feet, and an equal subsidence of the country south, and ima- 

 gine this whole mass converted by earthquake pulsations of the breadth 

 which such undulations have, into a series of stupendous and rapid- 

 moving waves of translation, helped on by the still more rapid flexures 

 of the floor over which they move, and then advert to the shattering 

 and loosening power of the tremendous jar of the earthquake, we shall 

 have an agent adequate in every way to produce the results we see, to 

 float the northern ice from its moorings, to rip off", assisted with its aid, 

 the outcrops of the hardest strata, to grind up and strew wide their frag- 

 ments, to scour down the whole rocky floor, and, gathering energy with 

 resistance, to sweep up the slopes and over the highest mountains. 



Perhaps I may be permitted, before quitting the class of topics con- 

 nected with geological dynamics, to allude to the researches upon which 

 this theory of earthquake action has been founded, and to refer to the 

 phenomenon which it is conceived to explain. 



At the last meeting of the Association, we deduced, from an analysis 

 of a large mass of data connected with the recent earthquakes of the 

 Mississippi valley and of the West Indies, and from the history of other 

 earthquakes, a striking confirmation of some of the laws of earthquake 

 motion long ago suggested by Mitchell. From the facts set forth, I 

 think it can no longer be doubted that a characteristic feature of earth- 

 quake motion is a rapid progressive undulation of the ground, of the 

 nature of a series of actual billows or waves, which are sometimes of 



