224) Prof. Hughes, Criticism of the Geological [Oct. 30, 



Part III. 

 The Evidence as to the extent of Earth movements, and 



THEIR RELATION TO GlACIAL PHENOMENA. 



To recall the line of argument followed. It is admitted that 

 we have abundant evidence of the local occurrence of land ice and 

 of the transport of material by sea-borne ice over areas where, 

 with the present geographical distribution and the existing climate, 

 glacial conditions do not and could not prevail. But the extent of 

 ice action has been pushed too far, and the recurrence of glacial 

 conditions in past time has been urged on insufficient and often 

 false evidence. The principal sources of error have been pointed 

 out, and some particular cases of wrong attribution to ice action 

 have been discussed. 



Having thus got rid of some of the difficulties which extreme 

 views of glaciation entail, we proceed to consider what geographical 

 conditions prevailed over certain areas where it is admitted that 

 glacial conditions did exist, or where the indirect influence of 

 neighbouring glaciation is shown to be probable. 



We find as the result of this enquiry abundant independent 

 evidence of repeated earth movements over the very areas indi- 

 cated by the distribution of glacial phenomena. 



There have been great upheavals where we see evidence of 

 increase of cold, great depressions where glaciated a,reas have been 

 brought down to sea-level in warm regions, and great complex 

 movements causing ocean currents to run where land had been, 

 or mountain ranges to rise where the tide had flowed. 



To this point I would now direct attention. Many collateral 

 questions of great interest naturally arise out of its discussion, 

 such as the continuity rather than the permanence of continental 

 and oceanic areas, &c. But I propose to confine myself to the 

 consideration of the evidence of the nature, amount, and effect of 

 the changes of level which can be proved to have taken place over 

 the areas where glacial conditions formerly prevailed. 



In examining the nature and extent of the geographical causes 

 of the more intense vicissitudes of temperature it may be well 

 at first to confine our attention to two principal basins, (1) the 

 North Atlantic basin, round which we have evidence of the severe 

 Pleistocene climate which is generally spoken of as the Glacial 

 Period, and on the existing shore of which the Conglomerates of 

 Cambrian, Carboniferous, and Poikilitic Age occur in which some 

 have seen proofs of ice action, and (2) the Indian Ocean, round 

 which it is maintained by many observers that evidence exists of 

 similar conditions having prevailed in times not long preceding 



