1847.] Meteorological Observations. 91 



to the warmer, and its return upon the approach of the opposite 

 season of the year. There would necessarily be two changes, 

 and such we have; at the approach of summer and on the verge 

 of winter, when the air would be calm and with little M'ind. 



The gradual transition of solar heat i'rom the northern to the 

 southern hemisphere, would be insufficient to cause an immediate 

 change in the prevailing direction of the winds, which would by 

 the momentum they had acquired, preserve their prevailing direc- 

 tion till long after the astronomical seasons had changed; other- 

 wise the change from south to north, would be so gradual as to 

 be insensible. Thus are the summer and the winter prolonged 

 beyond their iixed limits, and each is made to encroach upon the 

 other. Local and modifying causes may hasten or retard this 

 change in certain seasons and in certain localities; while particu- 

 lar districts may be so influenced by these causes, that the transi- 

 tion may be quite insensible. 



It is further to be observed, that the change would begin in the 

 equatorial regions and progiess gradually towards the poles, com- 

 mencing at about the time of the equinox, and causing those de- 

 structive storms that desolate the tropics at those periods of the 

 year. The change progressing slowly towards the polar regions, 

 would at length cease to be perceptible in high latitudes. Vari- 

 ous causes might delay the progress of the change, so that at the 

 same localities it might occur at an earlier or a later period, or 

 not perceptibly, according to circumstances. 



This cause is, in the opinion of the writer, sufficient to account 

 for the calm weather which usually precedes the commencement 

 of winter; the smoky and thick atmosphere of the Indian sum- 

 mer, must be accounted for on another theory. 



Its occurrence after the destruction of the herbage and foliage 

 by the frosts of autumn, (and in this region usually after our 

 early snows,) seems to indicate that it has some connection with 

 the annual destruction of vegetation, and that it is caused by the 

 fermentation and decay of vegetable matter. A fact in support of 

 this hypothesis is well known, viz: that the annual return of this 

 period, of late years, since the clearing up of the forests, has been 

 less decidedly characterized by a thick smoky atmosphere, than 

 in the early settlements of the country when a large amount of 

 vegetation was annually destroyed by frosts. 



In cultivated districts there is but a small amount of organic 

 matter thus destroyed, as most crops are removed before the oc- 

 currence of frosts; while the grass lands do not have their vege- 

 tation thus cut down. The halcyon days of antiquity, (which of 

 course continue down to the present time,) were spoken of as a 

 serene and sunny season when all nature was at rest, and the 

 stormy elements were lulled to repose. The air was of a delight- 



