MRTEDROI.OGY. 87 



smoke, arising from extensive lircs ilicu prevailing in our mountain for- 

 ests, on account of a considerable drought then existing. This state of 

 things was, at length, broken up by powerful and continued rains. From 

 tlie 2nd to the 16th of April, 1844, also a period of two weeks, a con- 

 dition of atmosphere existed, as remarkable in every respect, as the In- 

 dian Summer of November has ever been found to be. During every 

 year, however, perhaps without exception, this peculiar state of weather 

 may be noticed, more or less distinclly, at the time just named. 



A third case of similar condition of atmosphere is to be observed 

 from about the middle of January to its close, its duration is from eight 

 days to tvvo weeks. During this season, it not unfrequently happens 

 thai the farmers, in Pennsylvania and Maryland, plough the grounds 

 designed for the reception of their spring crops. Among the more re- 

 markable exami)le3 of this kind, may be cited the winters of 1817 and 

 '18, and those of 1S42 and '43. The January just passed has been ex- 

 traordinary for its mildness ; but, though having the usual amount of 

 smol:e in its atmosphere, being a part of a winter unusual in its charac- 

 ter from its connnencement to the first of the last month (Feb.), it does 

 not stjind contrasted with the rest of the season as other Januaries fre- 

 quently do. 



A fourtlh cnsc of that state of weather under consideration, occurs 

 during the month of August. The atmosphere has sunk into a state of 

 almost profound rest. The breezes, from the S. and S. W. which had, 

 almost daily, refreshed us during the months of June and July, and 

 wliich had thus rendered the heat less oppressive, have died away. The 

 almost stagnant and sultry air has its transparency destroyed by a thin 

 haze, through which distant objects appear as if tinged with the color 

 of smoke. Thunder clouds have diminished in frequency and in ex- 

 tent; and hence, except during extraordinary seasons, the month of Au- 

 gust is deficient in rain. The widely extended rain cloud does indeed 

 frequently cheer us with its refreshing showers, but these it distils rath- 

 er gently and quietly, and, after it has passed away, a dusky atmosphere 

 succeeds. This peculiarity of weather mostly occurs from the beginning 

 to the middle of the month. 



There are, therefore, agreeably to these views, four grand periods, at 

 which a smoky or hazy atmosphere pre-eminently prevails; viz. two of 

 greater intensity, occurring about a month or six weeks after the vernal 

 and autumnal Equinoxes ; and two of less intensity, or of less distinct 

 features, occurring at about the same length of time after the summer 

 and winter solstices. The autumnal is generally of the greatest inten- 

 sity, particularly so, as the immensp volumes of actual smoke wiiich are 



