274 Prof. Rogers's Address before the 



either of the more popular hypotheses of the day. This doctrine, ap- 

 peaUng to the proofs which our science furnishes of the sudden disturb- 

 ances of the level of the different tracts of the earth's surface, at all 

 periods of geological time, merely supposes that at the epoch of the 

 drift, the polar half of the northern hemisphere was the theatre of vio- 

 lent and perhaps frequently repeated movements of the earth's crust, 

 each particular disturbance emanating probably from a different local 

 region. These disturbances, which are conceived by Van Buch, De 

 Beaumont, Hopkins, De la Beche, Sedgwick, Phillips, and other dis- 

 tinguished geologists, to have been of the nature of simple paroxysmal 

 elevations^ and by my brother and myself to have consisted in an en- 

 ergetic and extensive undulation of the crust of the earth accompany- 

 ing each sudden rise, are deemed sufficient to have caused a rush of the 

 northern waters over all the higher latitudes of Europe and North 

 America, covering the surface with an almost continuous sheet of gravel 

 and bowlders, and polishing and scoring the whole rocky floor. 



The chief cause of hesitation with many minds in embracing a the- 

 ory so much in harmony with the general physical history of our globe, 

 has arisen from their not recognizing a force sufficient to dislodge and 

 sweep onward blocks of the huge size which we sometimes encounter, 

 or to drive the detrital matter up and over the high mountain barriers, 

 across which, by some process, it had travelled. So long as no definite 

 estimate has been made of the velocity of the current which would re- 

 sult from a given amount of paroxysmal elevation, such a distrust of the 

 energy of diluvial waters was natural and prudent ; but we are in pos- 

 session of facts and generalizations calculated greatly to exalt our con- 

 ceptions of this power. 



It has been shown by Mr. Hopkins, of Cambridge, reasoning from the 

 experimental deductions of Mr. Scott Russell upon the properties of 

 waves, that " there is no difficulty in accounting for a current twenty 

 five or thirty miles an hour, if we allow o? paroxysmal elevation of from 

 one hundred to two hundred feet ;" and he further proves that a cur- 

 Tent of twenty miles an hour ought to move a block of three hundred 

 and twenty tons, and since the force of the current increases in the 

 ratio of the square of the velocity, a very moderate addition to this 

 speed is compatible with the transportation of the very largest erratics 

 any where to be met with, either in America or Europe. 



Holding in view these demonstrable conclusions, let us consider the 

 far more enormous velocity which a broad general current would derive 

 from that mode of paroxysmal action, earthquake undulation, which 



