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Proceedings of the American Philosophical Society. 35 
form and velocity of the atmospheric wave, the progress of which, over 
the United States, he has represented upon a chart. 
2. A comparison of the observations of the thermometer and baromes 
ter shows, that while the pressure was diminishing the temperature was 
increasing, and vice versa. ‘The very remarkable diminution of tempe- 
rature of 48° Fah. in six hours and a half, occurred at one station in the 
N. W. of the United States. The commencement of the diminution of 
temperature is shown to coincide with the minimum of the barometer, 
and hence is used when barometric observations were not made, to point 
out the probable time of the occurrence of this minimum. The average 
of the maxima of the thermometer at the eastern stations was about 33° 
Fah. greater than at the western, and the average of the minima 14° Fah. 
greater. 
8. Rain or snow fell during the storm within the limits of about latitude 
28° N. to latitude 48° N., and from longitude 52° to96° W. The aver- 
age amount at fifty nine stations, was seven eighths of an inch. The 
author is led to remark upon the great discrepancies in the statements of 
the fall of rain at places very near each other, and upon defects in the 
registers in not stating the time of beginning and ending of the rain. 
4. The epoch of the minimum of pressure at the several places of ob- 
servation was marked by a change of wind from a southern quarter, gen- 
erally the southeast, to a northern quarter, almost uniformly the northwest. 
This southern change of wind was every where one of the most promi- 
nent features of the storm, the wind having been violent both before and 
after the change; but more violent from the northwesterly direction, ex- 
cept perhaps at New York and in the northeastern states. 
The author sums up thus the characteristic of the storm. After a cold 
and clear interval, with the barometer high, the wind commenced blow- 
ing from a southerly quarter ; the barometer fell rapidly, the thermometer 
rose, and rain fell in abundance. The wind subsequently veered sud- 
denly to the northwest, and blew with great violence; the rain was suc- 
ceeded by hail or snow, which continued but for a short time. The 
changes thus described occurred, not simultaneously, over the United 
States, but progressively from west to east. 
The author next endeavors to determine the limits of the storm, using 
for this purpose other meteorological registers in addition to those before 
Roticed, and of which he gives a particular account. From these, and 
theoretical considerations, he places the Rocky Mountains as the western 
limit, the parallel of 25° N. latitude as the southern limit, the middle of 
© Alantic as the eastern limit, and the northern as altogether conjectu- 
ral, but probably as remote as the arctic circle, thus extending over 70° 
= longitude and 40° of latitude. The question whether the remarkable 
which occurred in Europe about the 25th of December, was a con- 
tinuation of this storm, is examined, and the author concludes, from a 
