RECENT ADVANCES IN GEOLOGY. 461 
stride towards civilization. Ere long followed the discovery 
of the art of iron-smelting, —a discovery which has done 
more to advance the welfare of our race than all others com- 
bined. Then it was that man, for the first time, was fur- 
nished with a weapon which enabled him to achieve a 
conquest over Nature, and this assertion will not appear 
extravagant when we reflect how intimately this metal is 
connected with all the industrial arts. 
The Iron Epoch approaches so near the Historic Era, that, 
as forming a portion of geological history, the events are too 
insignificant to be dwelt upon. 
The Mound-builders of our own country, in the scale of 
civilization, were intermediate between the Polished stone 
and the Bronze Epochs of Europe. They resided in towns, 
many of which have since become the sites of flourishing 
cities. They practiced agriculture, making use of maize as 
their chief cereal; but there was not on this continent a 
domestic animal who could aid them in their labors or con- 
tribute to their sustenance. Strange as it may seem, that 
while the Danish kitchen-middins and the Swiss refuse-heaps 
contain abundant traces of mammalian bones, thus far they 
have been but rarely detected in the mounds. They chipped 
with great skill the limestone-chert into spades, spear- 
heads and arrowheads. Out of porphyry or greenstone 
they wrought their hatchets and battle-axes, and these were 
often ground and polished. The same material, too, was 
often used in making pipes, which were carved into forms 
representing quadrupeds and birds, so faithful in detail that 
the species to which they belonged can be identified. The 
specular iron-ore of Missouri was elaborately wrought and 
Polished into slung-shots or “plummets.” They mined ex- 
tensively the native copper of Lake Superior, which they 
beat, and perhaps smelted, into knives, chisels, spearheads, 
arrowheads and bracelets. They wove cloth with a regular 
Warp and woof, out of a fibre as yet undetermined. They 
modelled clay into vases, water-coolers, and othet utensils, 
