President's Address. 
321 
it may be safely asserted that during the historic period 
none of the animals above referred to were inhabitants of 
the southern and western portions of our continent. What- 
ever the date of these stone implements, and their asso- 
ciated mammoth and rhinoceros remains, they clearly belong 
to pre-historic times ; and the question is thus narrowed to 
the relative antiquities of certain events which occurred far 
beyond the reach of the oldest history and the remotest 
traditions. 
In dealing with pre-historic monuments, we may adopt 
either the methods of the archseologist, who founds chiefly 
on the comparative rudeness and simplicity of the relics, or 
those of the geologist, who looks mainly to the superposi- 
tion of the beds in which the relics occur, or those of the 
palseontologist, who argues from the specific differences of 
the flora and fauna ; or we may adopt a mixed method, and 
reason from all that archseologyj geology, and palaeontology 
supply. Adopting this latter plan, we reason from the lake- 
silts, peat-mosses, and deltic deposits containing stone im- 
plements and tree-canoes, associated with the bones of ex- 
tinct varieties of the horse and ox, back to similar deposits 
and cave-earths imbedding ruder implements and remains 
of the Irish deer, reindeer, and musk-ox, and from these 
again to deeper river gravels and brick-earths containing 
implements still simpler in fashion, and associated with the 
relics of mammoth and rhinoceros. Considerable changes 
in the physical geography of Europe must have taken place 
(as these silts and peat-growths imply) since the time of 
the primitive horse and long-fronted ox ; still greater must 
have taken place since the reindeer and musk-ox found a 
suitable climate in the latitude of France and England ; 
and greater still since the mammoth roamed in the pine 
forests and over the plains of the same regions. Admitting 
the changes, the question remains, How shall we estimate 
the lapse of time required for their fulfilment ? If they are 
changes of a physical kind, we estimate according to the 
rate at which similar changes are taking place at the present 
day; if of a vital kind, by the rate at which extinctions and 
creations seem to have been effected in former epochs ; and 
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