PHYSICAL AND CLIMATAL CONDITIONS. 143 



Siicli ])OC'uliarities of distribution serve to show tlie 

 efl'ects of civeii coiiiparativuly small cliaiiLces of level upon 

 climate, and upon the (Hstribution of life, and to eonfirm 

 the same lesson of caution in our interjirelation of local 

 diversities of fossils, wliieh geoloo-ists liavt' l)eon lately 

 learning from the distribution of cold and warm currents 

 in the Atlantic. Another lesson which they teach is the 

 wonderful fixity of species, (.'ontinenis rise and sink, 

 climates change, islands are devoured l»v the sea or 

 restored again from its depths: marine animals are locally 

 exterminated, and are enabled in the course of long ages 

 to regain their lost aljodes ; yet they remain ever the 

 same, and even in their varietal forms ])erfectly resemble 

 those remote ancestors which are sepanited from them liy 

 a vast lapse of ages and by many ])hysical revolutions. 

 This truth which 1 have already deduced from the I'leis- 

 tocene fauna of the St. Lawrence valley, is equally 

 taught l)y the molluscs of the Acadian bay, and l)y their 

 Arctic relatives returning after long al)sence to claim 

 their old homes. 



Still another lesson may be learned here. It a]»i)ears 

 tliat our ])rosent climate is se})arated fi'om that of the 

 glacial age by one somewhat warmer, wliicli was coinci- 

 dent witii an elevated condition of the land. Ajqjlied to 

 Europe, as it might easily l)e, this fact sliows tlie futility 

 of attem[)ting to establisli a later glacial period l)etwcen 

 the I'leistocene and the present, in the manner 

 attemj)ted, as I must think on the slenderest possible 

 grounds, by Prof. (Jeikie in his late work " The (Ireat 

 Ice Age." 



The grandeur of those physical changes which have 

 occurred since the present marine aninuds came into 

 being is well illustruied by some other facts to which our 



