ANNIVERSARY ADDRESS OF THE PRESIDENT. xlili 



down beneath its waters, clearly demonstrates the limitation of the 

 agency to which great foldings and contortions of stratified rocks 

 have been due to very confined spaces in each epoch. Were it other- 

 wise, the multiplication of such extensive convulsions during a long 

 succession of ages would have made it impossible to find any spot on 

 the globe where the oldest rocks had escaped extreme derangement. 

 It only remains therefore for the advocates of the paroxysmal hypo- 

 thesis to assert that, although the disturbing forces have by no means 

 grown feebler in the modern or tertiary times, as compared to pe- 

 riods when the oldest of the known strata were deposited, yet there 

 have been brief seras of convulsion on a very grand scale, when the 

 ordinary repose of nature was violently interrupted in particular re- 

 gions (as in the Alps, for example) in a manner wholly different, in 

 regard to the magnitude of the effects produced, from any which we 

 have witnessed in historical times, or which ever occurred formerly 

 during the ordinary and normal state of the globe. 



That doctrines of this kind are popular, I am well aware ; and if 

 you desire to know how many modern writers have declared in their 

 favour, I refer you to the excellent work which has just been pub- 

 lished by one of our foreign members, M. d'Archiac, on *The Hi- 

 story of the Progress of Geology from the years 1834 to 1845.' He 

 has executed conscientiously nearly half of the laborious and delicate 

 task assigned to him by the Geological Society of France, and has 

 given us a faithful digest of memoirs written in a variety of languages 

 and scattered through the Proceedmgs and Transactions of numerous 

 scientific bodies, or the periodical magazines and journals of almost 

 every civilized country. A geologist of practical experience in the 

 field, as well as of extensive erudition, was required to make a good 

 classification of such complex materials, and justly to appreciate their 

 relative value. In M. d'Archiac' s pages every author of merit has 

 been allowed an impartial hearing, and the expositor's own occasional 

 criticisms are not obtruded too prominentiv on he reader's attention ; 

 when they are offered, they are so judicious as to aid us materially in 

 understanding the faithful analysis he has given of the opinions of 

 others. In the concluding part of his chapter on " Le terrain mo- 

 derne," and when speaking of active volcanos, and in other places, 

 he stoutly denies the adequacy of the causes which have modified the 

 earth's crust in historical times to produce effects such as may enable 



VOL. VI. e 



