period, torn from its cliffs by some mighty glacier and slowly rolled and rounded, for hundreds of years perhaps, down the scarred slopes of its native valley.
THE GREAT EGG-SHAPED ROOK.
The primary cause of the intense and prolonged cold of the arctic regions is the shortness of the time during which they are under the influence of the sun’s rays. For a few months in summer the sun shines brightly, but, owing to the position of the globe, obliquely on the poles. During part of that period it shines at mid-night as well as at mid-day. But during the greater part of the year its beams throw but a feeble light there, and for several months in winter there is absolutely no day at all—nothing but one long dismal night of darkness, that seems as if the bright orb of day had vanished from the heavens for ever.
The length of this prolonged day in summer, and this dreary night in winter, depends, of course, upon latitude. The length of both increases as we approach the poles. The long daylight in summer is exceedingly delightful. We once saw the sun de-
