the New Zealand Alps, the
whole country would again be buried under glaciers pushing out into the
seas" on the west and east.

The theory is that as the climate became warmer, the ice-fronts
retreated northward by the shrinking of the glaciers, and therefore the
animals, including man, were able to live farther north. The men of that
very remote period were "Neolithic," and some of the stone monuments are
attributed to them that were formerly called "Druidic." A recent writer
asks; with reference to Stonehenge:

Did Neolithic men slowly coming northward, as the rigors of the
last glacial period abated, domicile here, and build this huge
gaunt temple before they passed farther north, to degrade and
dwindle down into Eskimos wandering the dismal coasts of arctic
seas?

Another writer, with reference to the American ice-sheet, says:

During the second glacial epoch when the great boreal ice-sheet
covered one-half of the North American continent, reaching as far
south as the present cities of Philadelphia and St. Louis, and the
glaciated portions were as unfit for human occupation as the
snow-cap of Greenland is to-day, aggregations of population
clustered around the equatorial zone, because the climatic
conditions were congenial. And inasmuch as civilization, the world
over, clings to the temperate climates and thrives there best, we
are not surprised to learn that communities far advanced in arts
and architecture built and occupied those great cities in Yucatan,
Honduras, Guatemala, and other Central American states, whose
populations once numbered hundreds of thousands.

An approximate date when this civilization was at the acme of its
glory would be about ten thousand years ago. This is established by
observations upon the recession of the existing glacier fronts,
which are known to drop back twelve miles in one hundred years.

With the gradual withdrawal of the glacial ice-sheet the climate
grew proportionately milder, and flora and fauna moved
simultaneously northward. Some emigrants went to South America and
settled there, carrying their customs, arts, ceremonial rites,
hieroglyphs, architecture, etc.; and an immense exodus took place
into Mexico, which ultimately extended westward up the Pacific
coast.

In subsequent epochs when the ice-sheet had withdrawn from larg