President's Address. 
319 
entombment, and are entitled to assign to them a still 
higher antiquity. In fact, we know that all changes in 
physical conditions, and all removals and extinctions of life, 
take place by slow and silent stages, and that the greater 
the difference between the "existing and the extinct, the 
longer must be the time that has elaped since their extinc- 
tion. By methods such as these we can establish a scale of 
old, older, oldest ; and there need be no more uncertainty 
about the results obtained by such methods than there is 
about the results obtained by the historian in modern, medi- 
eval, and ancient history. 
Another method by which we arrive at notions of relative 
antiquity is by the implements and works of art that occur 
in recent formations, or accompany the remains of man. 
We know the phases of modern, medieval, Eoman, Greek, 
Egyptian, and Babylonian art, and can assign something 
like a historical date to such objects and the accumulations 
in which they occur. We know, too, that man employs 
tools of wood and stone long before he learns the uses of the 
metals ; and that he reduces the softer metals, and works in 
copper and bronze, long before he has acquired the mastery 
over iron and steel. In this way we speak of the ages of 
stone^ bronze, and iron, the one preceding the other, and 
forming, as it were, a rude scale of time for the antiquarian 
and geologist. But while one nation may be working in 
iron, another more belated may be working in bronze, and 
a third, still more remote and savage, may be adhering to 
implements of wood and stone. To be of any use, this scale 
of stone, bronze, and iron must be applied to the same dis- 
trict ; and when so applied, archseologists are now pretty 
well agreed that it marks with considerable certainty the 
various stages of relative antiquity. Of course, were imple- 
ments of iron ever found along with remains of mammoth 
and mastodon, the scale would be utterly worthless ; but 
when stone tools invariably accompany the older remains, 
and those of bronze and iron those of younger and younger 
date, then we feel assured from this concordance of the im- 
plement scale with that of the animal that we have hit upon 
a pretty exact method, so far as Europe at least is con- 
