192 The American Geoloyixt. Murcii, isoa 
difficult to understand why be failed to roach and occupy so large 
an area as America, which seems to be as accessible then as now, 
or, at some periods, even more so. Negative evidence is proverbi- 
ally nntrustworth}' in geolog}', and we may yet come upon the 
trail of glacial man on this continent. 
So long as the astronomical theor}' of glacial climate prevailed, 
biologists hesitated to accept a doctrine which required them to 
assign a specific life to man of 80,000 years if only post-glacial, 
and of 150,000 if inter-glacial. So long a time, though possible, 
was against probabilit3^ But now that more moderate figures are 
being adopted, their reluctance to believe in post-glacial and 
glacial man is giving wa}", and they are more willing to allow the 
evidence. 
It is, however, still impossible to assign a date to glacial 
time. If the era was interrupted by a long inter-glacial spell of 
mild climate, when the ice entirely disappeared, higher figures are 
necessary than if the era was unbroken. On this point, the most 
energetic controversy now prevails. Granting the former and the 
inter-glacial date of man, or some anthropoid deserving that name, 
his age must be much greater than on the latter view, and yet need 
not be so great as to alarm the biologist. The enormous figures 
given by some are probably quite transcendental. Suspense of 
judgment and patience, are the proper states of mind in the 
present condition of the question. Positive statements, such as 
some that have recently appeai-ed, are entirel}' premature and un- 
warranted. 
Yet one word more. It is not likely that the evolution of man 
was sudden. If an anthropoid or several such intervened 
between him and the pithecoid branch from which he and his 
simian relatives have sprung, time must be allowed for the pro- 
cess of development. If then all the traces of worked or used 
stones thus far found are human indications, we must allow to 
mans semi-human ancestors, an earlier era in which they more or 
less slowly emerged from the brute. 
"When all these considerations are taken into account, there 
seem to be no valid objections to the existence of inter-glacial or 
of glacial man, ])ut on the other hand, strong grounds for antici- 
pating that his remains or traces will be found more abundantly 
and possibly of a date older than any yet met with. 
When the testimony of history is added, we may go one 
