ins 



274 Prof. Rogers's Address before the 



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

 pealing 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 

 Be°aumont, Hopkins, De la Beche, Sedgwick, Phillips, and other dis- 

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

 delations, and by my brother and myself to have consisted in an en- 

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

 ... & 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 an 

 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 e ni 

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

 sult from a given amount of paroxysmal elevation, such a distrus o 

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

 session of facts and generalizations calculated greatly to exalt our c 

 ceptions of this power. , 



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

 experimental deductions of Mr. Scott Russell upon the properties^o 

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

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

 one hundred to two hundred feet ;" and he further proves thai : aj^ 

 rent of twenty miles an hour ought to move a block of three 

 and twenty tons, and since the force of the current increases ro ^ 

 ratio of the square of the velocity, a very moderate addition o^ 

 speed is compatible with the transportation of the very largest err 

 any where to be met with, either in America or Europe. • , r t t, c 



Holding in view these demonstrable conclusions, let us const ^ 

 far more enormous velocity which a broad general current wou 

 from that mode of paroxysmal action, earthquake undulation, 



