A year among the trees

by Wilson Flagg

THE RED BIRCH.

The Red Birch is a rare species, and but very little known. By careless observers it might be mistaken for a white birch, the redness of its bark seeming only a departure from its usual type. The only trees of this species I have seen in Massachusetts were in Andover, in a swamp through which the Shawsheen River flows. If you would behold this tree to the best advantage, you must follow the streams that glide along the level woodlands which are inundated a part of the year. There it may be seen, like some pilgrim bending worshipfully over the stream, by whose beneficent waters it is sustained in beauty and health. Its picturesque attractions, arising from the great variety of its outlines and the peculiar wreathing of its foliage around the stem, are not surpassed by those of the willow, that delights in similar places. The reddish whiteness of the bark and wood has given the name to this tree. It is a tall, bushy tree of rapid growth, rolling up its bark in coarse ringlets, which are whitish with a stain of crimson.

THE INDIAN SUMMER.

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.