The Fall of the Leaf, 537 



casional solitary coreopsis in the meadows, or a blue-frirgod 

 gentian standing erect among the brown herbage of the 

 fields. But amid the general desolate appearance of nature, 

 the scarlet berries of the prinos are conspicuous among the 

 wild shrubbery ; and the wych-hazel, clad in a full drapery of 

 yellow blossoms, stands ready with joyful hues to welcome 

 the Indian Summer. 



The Indian Summer, which arrives during this third 

 autumnal period, if it comes at all, is a brief period of warm 

 weather that sometimes greets our climate in November, 

 after the fall of the leaf, and not as many suppose in October. 

 It is probably caused by the sudden check given to vegetable 

 perspiration, by the fall of the leaves. It is well known that 

 by sprinkling a floor, to cool a room in hot Aveather, we 

 cause the heat to be carried off with the evaporation of the 

 water. On the same principle, the infinite host of trees, 

 whose leaves are constantly evaporating the moisture of the 

 earth, must proportionally cool its surface, and the atmosphere 

 that is in contact with it. Anything that increases evapora- 

 tion from the earth's surface must cool it in the same manner. 

 Hence we may explain the greater coldness of the air over 

 valleys and wet places on summer evenings, and the fact, 

 often noticed, that a rainy spell in autumn is commonly suc- 

 ceeded by severe frosts. The greater burden of the foliage 

 of our woods remains on the trees and shrubs, until the 

 severe frosts in the latter part of October. About this time 

 the whole extent of our forests is often laid bare in the brief 

 space of a week or ten days. Not only does this great ex- 

 tent of surface, thus laid open to the sun, receive from his 

 rays an increased amount of heat, but there is a vast and sud- 

 den diminution, at the same time, of that evaporation which 

 is caused by the leaves of plants. These two circumstances 

 unite in producing, when no outward agencies interfere, a 

 great accumulation of heat. The warm spell that follows is 

 the true Indian Summer, and may last from five to eight 

 days. During one of these spells of fine weather, I have 

 sometimes heard the crickets chirping merrily as late as the 

 eighteenth of November. 



VOL. XIX. NO. XII. 68 



