ABOUT THE 20tH OF DECEMBER, 1836. 151 



were light, and their directions very various. More usually they were from 

 the west, the quarter from which they had blown with great strength the day 

 previous; but at a few stations they had already changed to the south and east, 

 which was soon to become the prevalent direction; for it appears there was now 

 a barometric minimum, not far to the west, towards which the whole atmo- 

 sphere soon precipitated itself with great violence. In the afternoon of the 18th 

 there was no change in the wind's direction at any station east of Detroit, nor 

 any change of importance on the southern border. On the north-west the wind 

 generally veered round more to the south, the cause which I have already as- 

 signed becoming now more sensible in its operation. 



On the morning of the 19th, the wind, at places east of Baltimore, was still 

 from the west. Albany furnishes the only exception to this remark, and here 

 the wind is from the south. On the southern border the wind still blew from 

 the north. At Picolata only was it from the east. In the western and north- 

 western states it was from the south. To this there was but one exception, at 

 Fort Brady, where the wind was north-east. The more general tendency was 

 from the south-east. A very instructive phenomenon is here exhibited. The 

 barometer was at its maximum height on a line passing north and south, nearly 

 through the centre of the United States, and the wind accordingly blew out- 

 ward from the centre every where upon the borders. I do not mean precisely 

 in the direction of radii from one point, but still decidedly outward; and there 

 is but one palpable exception to this remark, namely, at Alleghany Arsenal, 

 where the wind is reported from the north. Thus, on the eastern border, the 

 prevalent direction was westerly; on the southern, northerly; on the western, 

 south-easterly; and on the northern, southerly. These currents could not be 

 maintained without producing a rapid drainage of air from the United States, 

 unless there were some means of compensation. In point of fact, the drainage 

 was not very rapid, as is shown by the barometric observations, and the re- 

 quired compensation we shall find in the upper current of the atmosphere. 

 The winds of which I have been speaking were surface winds, reaching to 

 only a moderate elevation, and above them flowed the usual upper current from 

 the west. This might have been safely presum.ed in the absence of all testi- 

 mony. The fact vv-as, however, observed at Springfield, Syracuse, and 'Hev^^ 

 York, the only journals which noted at this time the direction of the clouds. 

 The drainage from the lower currents was, however, somewhat more rapid 



