s
in the surface, to form the lakes which everywhere abound over Northern
territories. Some glacialists even hold the view first suggested by
Ramsey, of the British Geological Survey, that the great glacial sheets
scooped out the basins of many lakes, including the system that feeds
the St. Lawrence. At all events, it left traces of its presence all
along the line of its retreat, and its remnants exist to this day as
mountain glaciers and the polar ice cap. Indeed, we live on the border
of the last glacial epoch, for with the closing of this period the long
geologic past merges into the present.

PAST, PRESENT, AND FUTURE

And the present, no less than the past, is a time of change. This is the
thought which James Hutton conceived more than a century ago, but which
his contemporaries and successors were so very slow to appreciate. Now,
however, it has become axiomatic--one can hardly realize that it was
ever doubted. Every new scientific truth, says Agassiz, must pass
through three stages--first, men say it is not true; then they declare
it hostile to religion; finally, they assert that every one has known
it always. Hutton's truth that natural law is changeless and eternal
has reached this final stage. Nowhere now could you find a scientist
who would dispute the truth of that text which Lyell, quoting from
Playfair's Illustrations of the Huttonian Theory, printed on the
title-page of his Principles: "Amid all the revolutions of the globe
the economy of Nature has been uniform, and her laws are the only things
that have resisted the general movement. The rivers and the rocks, the
seas and the continents, have been changed in all their parts; but
the laws which direct those changes, and the rules to which they are
subject, have remained invariably the same."

But, on the other hand, Hutton and Playfair, and in particular Lyell,
drew inferences from this principle which the modern physicist can by no
means admit. To them it implied that the changes on the surface of the
earth have always been the same in degree as well as in kind, and must
so continue while present forces hold their sway. In other words, they
thought of the world as a great perpetual-motion machine. But the
modern physicist, given truer mechanical insight by the doctrines of the
conservation and the dissipation of energy, will have none of that. Lord
Kelvin, in particular, has urged that in the periods of our earth's in
fancy and adolescence its deve