196 



2. A comparison of the observations of the thermometer and baro- 

 meter, shows that while the pressure was diminishing the temperature 

 was increasing, and vice versa. The very remarkable diminution of 

 temperature 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 dimi- 

 nution 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 3^° Fah. greater than at the western, and 

 the average of the minima 14° Fah. greater. 



3. Rain or snow fell during the storm within the limits of about 

 latitude 28° N. to latitude 48° N., and from longitude 52° to 96° W. 

 The average 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 

 observation was marked by a change of wind from a southern quar- 

 ter, generally the south-east, to a northern quarter, almost uniformly 

 the north-west. This sudden change of wind was every where one 

 of the most prominent features of the storm, the wind having been 

 violent both before and after the change ; but more violent from the 

 north-westerly direction, except perhaps at New York and in the 

 north-eastern states. 



The author sums up thus the characteristic of the storm. After a 

 cold and clear interval, with the barometer high, the wind commenced 

 blowing from a southerly quarter; the barometer fell rapidly, the 

 thermometer rose, and rain fell in abundance. The wind subsequently 

 veered suddenly to the north-west, and blew with great violence ; the 

 rain was succeeded 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 endeavours to determine the limits of the storm, 

 using for this purpose other meteorological registers in addition to 

 those before noticed, and of which he gives a particular account. 

 From these, and theoretical considerations, he places the Rocky Moun- 

 tains as the western limit, the parallel of 25° N. lat. as the southern 

 limit, the middle of the Atlantic as the eastern limit, and the northern 



