President* s Address. 
323 
associated with the bones and tusks and horns of these ex- 
tinct mammalia. But these implements (like those of 
Abbeville, &c.) are often found at great depths, and at alti- 
tudes above the levels of existing rivers that prove the 
occurrence of great physical changes in these regions ; and 
this, taken in conjunction v^ith the extinction of the mam- 
malia and the evident amelioration in climate, bespeaks a 
vast antiquity compared with the shell-mounds and pile- 
dwellings of the preceding races. A vast antiquity! but 
whether ten, twelve, or twenty thousand years, w^e have in 
the mean time no mode of precisely determining. 
Physical changes proceed at rates too uncertain to con- 
stitute a scale of chronology, and we know too little of the 
law of vital development to found upon the duration and 
extinction of species. But if we may judge from existing 
operations, and if we may estimate from the specific changes 
in life now going on around us (and this with all the inter- 
fering influences imposed by man), then the time must be 
vast indeed since these primitive races were the inhabitants 
of Southern and Western Europe. We do not contend, like 
some, for thousands of centuries ; but we argue for triple or 
quadruple the amount that has hitherto been assigned to 
human chronology. Let us look fairly at the facts : the 
river-drifts, cave-earths, and lake-silts are, no doubt, very 
ancient, but there is nothing connected therewith that may 
not (computing by existing operations) have been accom- 
plished in ten or twelve thousand years. Again, the mam- 
moth, woolly rhinoceros, cave-lion, cave-bear, and cave-hyena, 
are but species of existing genera ; and so little do they 
vary in general character from those still living, that their 
appearance at the present day would excite no marvel. The 
whole aspects and surroundings of these extinct mammalia 
are in truth geologically recent ; and when we further con- 
sider the fresh condition in which some of them occur in 
the ice-gravels of Siberia, we are compelled to withhold 
from them an unlimited antiquity. It is a sound maxim in 
palaeontology, that the greater the divergence of any species 
from existing species, the greater its antiquity ; and found- 
ing on this rule, the mammoth, mastodon, and their huge 
