In heavy gales, the neighbourhood of a solitary tree is a positive nuisance.  It creates a violent eddy of wind, that leaves palpable evidence of its existence.  Thus, in corn-fields, it is a common result of a storm to batter the corn quite flat in circles round each tree that stands in the field, while elsewhere no injury takes place.  This very morning that I am writing these remarks, November 158, I was forcibly struck by the appearance of Kensington Gardens, after last night’s gale, which had covered the ground with an extraordinary amount of dead leaves.  They lay in a remarkably uniform layer, of from three to five inches in depth, except that round each and every tree the ground was absolutely bare of leaves for a radius of about a yard.  The effect was as though circular discs had been cut out, leaving the edges of the layer of leaves perfectly sharp and vertical.  It would have been a dangerous mistake to have slept that night at the foot of any one of those trees.

Again, in selecting a place for bivouac, we must bear in mind that a gale never blows in level currents, but in all kinds of curls and eddies, as the driving of a dust-storm, or the vagaries of bits of straw caught up by the wind, unmistakably show us.  Little hillocks or undulations, combined with the general lay of the ground, are a chief cause of these eddies; they entirely divert the current of the wind from particular spots.  Such spots should be looked for; they are discovered by watching the grass or the sand that lies on the ground.  If the surface be quiet in one place, while all around it is agitated by the wind, we shall not be far wrong in selecting that place for our bed, however unprotected it may seem in other respects.  It is constantly remarked, that a very slight mound or ridge will shelter the ground for many feet behind it; and an old campaigner will accept such shelter gladly, notwithstanding the apparent insignificances of its cause.

Shelter from the Sky.—­The shelter of a wall is only sufficient against wind or driving rain; we require a roof to shield us against vertical rain, and against dew, or what is much the same thing, against the cold of a clear blue sky on a still night.  The temperature of the heavens is known pretty accurately, by more than one method of calculation:  it is -239 degrees Fahr.; the greatest cold felt in the Arctic regions being about -40 degrees Fahr.  If the night be cloudy, each cloud is a roof to keep off the cold; if it be clear, we are exposed to the full chill of the blue sky, with only such alleviation as the warming and the non-conducting powers of the atmosphere may afford.  The effect is greater than most people would credit.  The uppermost layer of the earth, or whatever may be lying exposed upon it, is called upon to part with a great quantity of heat.  If it so happen that the uppermost layer is of a non-conducting nature, the heat abstracted from it will be poorly resupplied by communication