154 ON THE STORM EXPERIENCED THROUGHOUT THE UNITED STATES 



order to present these changes more palpably to the eye, I have drawn upon 

 the chart arrows, representing the direction of the wind for the forenoon of the 

 21st, the length of the arrow being intended to be proportioned to the strength 

 of the wind. These observations were not all strictly cotemporaneous ; and 

 hence arises some confusion in the course of the winds near the line of baro- 

 metric minimum, particularly in the state of New York. It cannot, however, 

 fail to be perceived that, at places moderately removed from each other, the 

 wind blew from quarters almost diametrically opposed. At a little distance 

 from the hne of barometric minimum, on the east, the wind was from the 

 south-east, while, on the west, it blew from the north-west. These were both 

 violent winds, whose velocity, probably, could not be estimated at less than 

 forty miles per hour. But how is it possible for two winds, not far separated 

 from each other, to blow violently towards each other for hours, and even days, 

 in succession? Let us make a simple numerical estimate. The wind blew 

 from the north-west at least forty miles per hour. This gives a progress due 

 east of more than twenty -eight miles per hour, and is fully equal to the average 

 progress of the barometric minimum. This atmospheric wave, then, progressed 

 with not far from the velocity with which the wind was actually observed to 

 blow. But, in order to allow an opportunity for this onward progress, the 

 wind in advance of this wave must retire, and that with the same velocity 

 with which the north-west wave approaches. There seems no other possible 

 supposition, unless the north-west wind flowed under the opposing wind. But 

 what was the motion of the air in advance of this wave? About six hours in 

 advance, it blows from the south-east; then, for three or four hours, it blows 

 nearly from the south, and the entire change from south to north-west occupies 

 only from one to two hours. The whole body of air in advance of this wave is 

 moving, then, in almost exactly an opposing direction; whereas, as I have 

 already stated, it ought to move in the same direction, in order to allow the 

 wave's onward progress. The conclusion is inevitable; the north-west wind 

 displaces the south-east one by flowing under it. I can think of but one mode 

 in which any one can imagine it possible to evade this conclusion. The wind 

 changed from south-east to north-west by the south-west. Some might fancy, 

 therefore, that this south-west wind might furnish the necessary vent for this 

 surplus air. But this south-west wind seldom blew an hour at any one place. 

 Now, the phenomena which I have described were occurring simultaneously 



