ANNIVERSARY ADDRESS OF THE PRESIDENT. XXV 



reasons I have determined to make this subject the leading one of 

 my address. In doing so I shall not restrict myself to a mere ana- 

 lysis of the communications which have been made to us. I shall 

 venture to criticize them with such freedom as may, I trust, require 

 no further apology than that which the desire of advancing our science 

 may afford. I shall also, before I enter on this more detailed analy- 

 sis, endeavour to bring before you a general \'iew of some of the more 

 important parts of the subject, under the aspect which it now pre- 

 sents to us. Papers also on other subjects have been brought before 

 us, which are far too important to be omitted in any general review 

 of our proceedings, and to which I shall in the sequel direct your 

 attention. 



If the period of the Drift involved only a repetition of the action 

 of those geological causes which we recognize in earlier geological 

 periods, it would still have an especial interest, as approximating to 

 our own times, and as less likely than those earlier periods to have 

 the nature and character of its operations and phsenomena masked 

 by those of succeeding periods. But besides this, we have reason to 

 regard it as a period of peculiar conditions, and of phsenomena refer- 

 able to peculiar causes, the study of which has opened to us entirely 

 new views respecting the agencies which have so marvellously modi- 

 fied the face of our planet, by the continual transference of matter 

 from one part of its surface to another. The study of this period 

 has also led us to a knowledge of climatal conditions not before sus- 

 pected, and to various researches into the causes which may have pro- 

 duced those conditions ; and thus we have extended our knowledge 

 of one of the most interesting branches of terrestrial physics. 



There is perhaps no branch in which speculative geology has re- 

 cently made more satisfactory progress, than in theoretical views re- 

 specting the agencies by which the larger masses associated wdth the 

 Drift, the erratic blocks, have been transported from one locality to 

 another. At the same time no subject, perhaps, has been more cha- 

 racterized, in passing through its various phases, by extreme hypo- 

 theses and premature conclusions. "When water alone was recognized 

 as the means of transport, hypotheses were sometimes made respect- 

 ing the magnitudes of single waves, and their passage even over ele- 

 vated mountains, which nearly all of us should now agree in con- 

 demning as extravagant ; and effects were attributed to them which, 

 from the transitory character of any single wave, were not only im- 

 probable, but perhaps physically impossible. In the abandonment 

 of such extreme hypotheses we have made a most salutary step. 

 Nor was the introduction of the glacial theories of transport by gla- 

 ciers and floating ice, unattended by hypotheses, which might be 

 deemed extreme hypotheses with as much propriety as those which 

 were condemned as extravagant in the agency of water. It is mani- 

 fest, however, that these extreme views are gradually but surely giving 

 way in favour of those more moderate, and as I believe sounder views 

 to which we appear to be rapidly converging. 



The glacial theories of transport of erratic blocks made rapid pro- 

 gress among us soon after their first announcement, although received 



