Our earth is a fairly comfortable little world in spite of the fact that its warmth comes from a furnace 92,000,000 miles away. It is true that its two polar ends are icy, but if the winter is too cold in New York we can go south to Miami or Panama or Colombia and find as warm a climate as we want.
We are apt to think that our present conditions are normal, but that is far from being the case. Our temperatures are far below the usual conditions shown by fossils in the world’s past history. More than a quarter of a century ago I climbed a mountain in Spitzbergen, crossing a snow-field and a glacier, to reach beds of sandstone crowded with great fossil leaves of a forest as luxuriant as those of southern New York or Pennsylvania. The tallest willow or birch on Spitzbergen now rises less than