INVESTIGATION OF STORMS. 179 



side than on the west. For if the storm had moved towards 

 the east with the same velocity as the west wind, it is man- 

 ifest that none of the wind on the western side of the cen- 

 tral line would have ascended, and if the storm moved with 

 half the velocity of the western wind, then only half the 

 western wind would ascend, &c. For example, suppose the 

 storm moved towards the east sixteen miles an hour, and 

 the wind blew inwards on each side with a velocity of forty- 

 eight miles an hour, then thirty-two miles an hour would 

 ascend on the west side, and sixty-four miles an hour would 

 ascend on the east side. It is easy to see why much less 

 should ascend on the western or rather northwestern side 

 than on the south-eastern ; it is because of the much greater 

 degree of cold on the north-western side of the storm. The 

 air on the north-western side of the central line will there- 

 fore be specifically heavier both on account of greater cold 

 and a lower dew point. It seems probable also that this 

 heavier air will have a tendency to cause the storm to move 

 more to the southward, than it would independent of this 

 influence. But many more observations on the motions of 

 storms must be made, before we can pronounce with cer- 

 tainty to what extent these theoretical deductions are cor- 

 rect. 



Perhaps it may be found, that when the north west wind 

 is excessively cold it will not ascend at all, and then the 

 motion of the storm will be equal to the velocity of the west- 

 ern or northwestern wind. 



139. A violent gale of this kind seems to have occurred 

 on the morning of the 23d, a few days before. This gale 

 commenced at Springfield, Ohio, about 10|, P. M. of 22d, 

 reached Lancaster, Pa. at 7h. 10m., Reading about 7h., 

 and Philadelphia about 20 minutes before 9, A. M. This 

 gale was preceded by no south east wind, at least at Phila- 

 delphia, and Lancaster, and Springfield, but it was every 

 where in Pennsylvania accompanied by a furious snow 



