460 RECENT ADVANCES IN GEOLOGY. 
The reindeer, the musk-ox, and the elk, migrated to the 
north where the changed conditions of climate were more 
congenial to their nature. 
The musk-ox has disappeared from Europe, but he sur- 
vives on this continent, restricted in his range to what are 
known as the “Barren Grounds,” lying between the Wel- 
come and Coppermine mountains. The auroch, protected 
by stringent laws, still survives, while the horse, domesti- 
cated by man, has vastly multiplied. . The ure-ox, living 
through the great catastrophe, has disappeared within his- 
torical times. 
The greatly augmented thickness of the Loess on this con- 
tinent, would indicate that the ice action was exerted more 
powerfully, and its effects are traced over a larger area; and 
the same destruction overtook the larger quadrupeds, extend- 
ing even to the gigantic sloths, who lived in a milder cli- 
mate. 
From this era we may date a change in the physical con- 
ditions of our planet, so far at least as relates to the north- 
ern temperate zone. The climate became milder, and the 
soil yielded more bountifully those seeds and fruits which 
contribute to human support. Man for the first time began 
to show signs of progress in the industrial arts. His weap- 
ons of flint were more symmetrically fashioned, and in some 
instances were polished. The dog became his companion, 
and some of the other animals were domesticated. This 
was the Polished stone Epoch. 
n the Bronze Epoch we trace still greater advances. 
Man dwelt in fixed habitations. He surrounded himself with 
such domestic animals as the ox, horse, pig, goat, and sheep, 
and retained his companionship for the dog. He cultivated 
wheat and barley, whose flour he kneaded into bread and 
baked between heated stones. Apart from berries he gath- 
ered the fruits of the pear, cherry, and plum. The discovery 
of the art of smelting copper, and of the additional art of 
hardening it by a slight admixture of tin, was an immense 
