Note 5 — Chapter IV

Many readers will regard this climate quite bearable, inasmuch, as in our own day regions may be cited whose mean temperature is much lower, yet which are nevertheless habitable, as, for example, Verchnoiansk, whose mean annual temperature is –19.3°. But in these regions there is a summer during which the ice melts; and if in January the temperature falls to –60°, and even lower, in July they enjoy a temperature of fifteen and twenty degrees above zero. But at the stage which we have now reached in the history of the world, this mean temperature of the equatorial zone was constant, and it was impossible for ice ever to melt again.