When November arrives, leading along with it the short days and the
darkness of winter, it opens the windows of the deep woods, pervaded all
summer by a sort of artificial twilight. The general denuded state of
the forest admits the sunshine into its interior, and brightens it with
a cheerfulness exceeding that of any other season. Some light-tinted
leaves still remain upon the trees which have been screened by their
situation from the frost and the wind, and many an interesting object is
exposed to view which was concealed by the foliage in summer. A few
asters and gentians still linger in some protected nook, and the
chickadees and hemp-birds make the wood lively by their garrulity and
their motions. The ground is covered with red, brown, and yellow leaves,
making a pleasant carpet for our feet, and increasing all the pleasures
of a woodland ramble.
After the fall of the leaf is completed, then, according to tradition,
comes the Indian Summer,—a fruitful theme both for poets and
philosophical writers, but of which no one knows anything from
experience. It may, after all, be only a myth, like the halcyon days of
the ancients, the offspring of a tradition that originated with certain
customs of the Indian, and which occasional days of fine weather in the
autumn have served to perpetuate. It is certain that we have now in the
Eastern States no regular coming of this delightful term of mildness and
serenity, this smiling interruption of the melancholy days of autumn. We
are greeted occasionally by two or three days resembling it after the
first cool weather of October, and these short visits are in some years
repeated several times. But a true Indian Summer, attended with all the
peculiar phenomena described by some of our early writers both in prose
and verse, rarely accompanies a modern autumn. It has fled from our land
before the progress of civilization; it has departed with the primitive
forest. I will, however, for the present, set aside all my conjectures
of its mythical character, and treat it as a matter of fact.
The Indian Summer, if such a season was ever known, was a phenomenon
produced by some unexplained circumstances attending the universal
wooded state of the country that existed for many years after its
settlement. According to the most apparently authentic accounts, it did
not arrive until November, nor until a series of hard frosts had
destroyed all the leaves of the forest. It then appeared regularly every
year. At the present time people know so little about it that they
cannot name the period of the autumn when, if it were not a thing of the
past, it should be expected. Will the disappearance of this phenomenon
admit of a philosophic explanation? Let us consider some of its probable
causes, and the effects of the changes which have taken place in our
land.
It has been observed that a meadow covered with luxuriant grass and
other herbage cools the atmosphere that rests upon it much more rapidly
than a similar meadow covered with a scanty herbage. The moisture
exhaled into the air by vegetable perspiration is greater than from any
other natural surface; and as the radiation of heat is rapid in
proportion to the moist condition of the atmosphere, the cooling process
over a grassy meadow is vastly greater than over a similar ground bare
of vegetation. A wood, in like manner, by exhaling through its foliage
the moisture it draws from the earth, cools the atmosphere in proportion
to the amount of its foliage, while at the same time it shades the
ground from the sun. Anything that should check this vegetable
perspiration would in the same ratio preserve the heat of the atmosphere
by diminishing the radiation of heat that takes place more slowly in dry
than in moist air.
This is precisely what happens soon after the first severe frosts of
November, when the whole extent of the forest over thousands of miles is
laid bare in the brief space of two or three days. There is a sudden and
universal diminution of the moisture that was given out from the leaves
of trees and other plants before the frost had destroyed them; for the
evaporation caused by the drying of fallen leaves and herbage is
comparatively slight, and ceases after a few hours’ exposure to the sun.
The atmosphere being dry, and the radiation of heat proportionally small
in quantity, all these circumstances, if no unusual atmospheric
disturbances occur from any other hidden cause, unite in producing a
sudden and universal accumulation of heat. The warm period that follows
is the Indian Summer.
A writer in “Silliman’s Journal” of 1833, who advances a very different
theory to explain this phenomenon, makes a statement that favors my
view: “It appears to us that the existence and duration of the Indian
Summer in this country has an important connection with the extensive
forests and uncultivated lands peculiar to America. And it is worthy of
remark, that, according to the recollection of the oldest of our
inhabitants, its former duration was often three or four weeks; whereas
its present continuance is short and uncertain, seldom exceeding ten or
fifteen days. It appears also that this decline has been somewhat
regular, keeping pace with, and evidently influenced by, the gradual
uncovering of the country.”
It is surprising that the writer, after making these observations,
should resort to some unintelligible reasoning about the trade-winds,
and certain assumed electric phenomena, to account for the Indian
Summer. I can easily believe that before the encroachments upon the
American forest were very extensive, this halcyon period of autumn may
have occurred every year with great regularity. But since the clearing
is almost universal, these conditions have been entirely changed. During
the primitive state of the forest, its sudden denudation produced a more
complete revolution on the face of the country than could possibly
happen at the present time. The clearing of the woods has also cast down
the barriers that impeded the circulation of the winds; at present these
winds, sweeping freely over the continent, would counteract any
influences, whatever they might be, that would produce an Indian Summer
in any locality.
The true Indian Summer was a period of very mild weather, lasting from
ten to fifteen days, and accompanied neither by wind nor rain. It has
been incorrectly described by certain writers as attended with fog. The
sky, though somewhat dim, was not obscured by vapor, but by a sort of
ruddy haze, that veiled the prospect, as it often will during a series
of warm, still days happening at any season. I draw my inferences from
what I have reason to consider the most authentic accounts. The air was
dry; and it could not have been otherwise. If it were moist, the
increased radiation would soon dissipate the heat and put an end to the
Indian Summer, which was never known to survive a copious and extensive
fall of rain. The atmosphere was described as being obscured by smoke,
rather than vapor, and this was most apparent in the latter part of the
day. This smoky atmosphere has led some writers to suppose the whole
phenomenon to be caused by fires in the woods.
According to tradition, no part of the year was more delightful than
this short period. Those accounts, however, that extended its duration
beyond the space of fourteen or fifteen days were undoubtedly
exaggerated. The nearest approaches to an Indian Summer which I have
witnessed in its proper season have never lasted a week. In our day,
when a warm week occurs in the autumn, it comes at no regular or
expected time. This irregularity of its occurrence proves that it is not
to be identified as the Indian Summer, which was regular in its
happening immediately after the entire denudation of the forest. Similar
but shorter periods of mild and serene weather may happen, at the
present epoch, in winter and spring as well as in autumn. These
irregularities of the weather cannot be explained; nor can we make
predictions of the time when any of them may happen. But a warm period
in October or December or January is not an Indian Summer, which
belonged to November, and is only a relic of the past.
The origin of the name is explained by Dr. Lyman Foot, in the third
volume of “Silliman’s Journal.” He says: “If you ask an Indian in the
fall when he is going to his hunting-ground, he will tell you when the
fall summer comes, or when the Great Spirit sends our fall summer;
meaning the time in November which we call the Indian Summer. And the
Indians actually believe that the Great Spirit sends this mild season in
November for their special benefit.”