822 
THE CANADIAN NATURALIST. 
winter ; for in our frigid clime, we are glad of any shorten- 
ing of our winter of half the year. I do not know that this 
little mimic summer ever fails of its appearance, though in 
some seasons it is much more brief in its duration than in 
others. Sometimes it continues, a course of beautiful and 
serene weather, for two or three weeks ; at others, we have 
only as many days, hastily snatched from the sway of Boreas, 
just to remind us of balmier times. 
C, — It is a pleasant variation, and as curious as it is 
agreeable. Pray what is the cause of the phenomenon ? 
F. — I believe no adequate cause has yet been assigned, 
though many conjectures have been hazarded. Some have 
supposed the heat and mist to be evolved by the fermenta- 
tion of those immense masses of vegetable matter, leaves of 
trees, wild herbage, &c., which are deposited at this season, 
over the vast forests and wildernesses of this continent. 
But it appears to me that fermentation would take place to 
a much greater extent in the ensuing spring 'than in the 
autumn, the heat of that season being likely to have a 
greater effect on these masses, especially after their having 
been saturated with moisture from the melting snows, which 
have lain upon them through the winter. Others conjecture 
that the heat and haze are caused by the fires which at this 
season are kindled on almost every farm to consume logs, 
brush, &c., after the drying of summer. This cause, at first 
sight, seems very incompetent to the production of so general 
an appearance ; but the burnings appear to be very widely 
spread, and I have myself observed at other times, when 
large brush fires have been burning in the neighbourhood, 
that the smoke will be diffused and rest in the air for several 
days, if there be no wind, causing an appearance very simi- 
lar to the present. Still, however, I incline to think that it 
owes its origin to natural, rather than to artificial causes. 
C. — The lepidopterous insects seem glad to avail them- 
