12 THK K'K A(iH IX CANADA. 



liciit, adviiiitimcs which imist liiive oxisled to a less extent 

 ill western Imiioiic* 



" It is t'lirihcr to lie ol)S('r\('(l tliat siicli subsidence and 

 eleviitiou would lu'ccssaiily allord threat facilities for the 

 nii^irratioii of avdic inariiu' auinials, and that the din'er- 

 eiici! lictwecu inoilcrn and ])leistoc('iie faunas must be 

 greatest in those localities to which the animals of 

 temperate reiiions could most readily minrute after the 

 chalice of temperature had occurred." 



In an address delivered in 18G4t as reliriiiu: president 

 of the Natural History Society of Afontreal, the relative 

 importance of land-ice and sea-borne ice is referred to in 

 the foliowinu' terms, in connection with the then recent 

 tipi)earance of Lou'an's "(leneral Keixirt on the (Jeology of 

 Canada," published in ISIil!: — 



" Tliere is another subject of ,u;reat geological importance 

 on which the i)ublication of this rt'port enables strong 

 ground to be tid-ceii. F refer to the conditions under 

 which the hDiiUlcr-driff of Canada was deposited. It 

 has been customary to refer this to the action of ice-laden 

 seas and currents, on a continent first subsiding and then 

 re-elevated. Ihit this opinion has recently l)een giving 

 way l)efore a re-assertion of the doctrine that land- 

 glaciers have been the principal agents in the distributiim 

 of the boulder-drift, and in the erosions with which it was 

 accompanied. I confess that I have steadily rejected this 

 last doctrine; being convinced that insu})erable physical 



* One cannot be too enipliatic in insisting on the fact that, in Nortli 

 America, tliroughout geological time, movements of subsidence which 

 threw open the interior plains to the arctic currents produced refriger- 

 ation, while those that produced a great mediterranean sea, open to 

 the south and closed on the north, introduced mild climates. 



t Canadian Naturalist, 18(J4. 



