114 Observations on the Storm of Dec. 15, 1839. 



which pertain, more or less, to many of the storms or gales that 

 visit the United States and other regions. These characters have 

 claimed attention from almost the earliest period of my inquiries. 



1. The body of the gale usually comprises an area of rain or 

 foul weather, together with another, and perhaps equal, or greater 

 area of fair or bright weather, 



2. The fall of rain or snow often extends, in some direction, 

 greatly beyond the observed limits of the gale. 



3. The gale itself not unfrequently exhibits an apparently un- 

 equal extent of action, or degree of violence, on different sides of 

 its apparent axis of rotation. 



This peculiarity, as well as the second, is most common in 

 winter storms, and in those which sweep over an extensive con- 

 tinental surface ; and, like other irregularities, is less noticeable 

 in the storms which are traced solely on the ocean. 



4. The barometric indications of a gale commonly extend 

 much beyond the observed limits of its action. 



5. The body of the gale constitutes a determinate sheet or 

 stratum of moving air ; and of this sheet or stratum a large por- 

 tion sometimes overlies another and more quiescent stratum of 

 air, the latter having, perhaps, a different motion ; as may be of- 

 ten observed in the common winds of the temperate and higher 

 latitudes : in which case the gale is either not felt at the surface 

 of the earth, or the observed changes of wind are found, in part, 

 unconformable to the whirlwind theory. 



6. Owing to the convergent and somewhat variable courses of 

 storms in the extra-tropical latitudes, as well as to their unequal 

 rates of progress, two storms will sometimes cover, in part, the 

 same field, one of which will overlie the other, and, perhaps, 

 thin out at its margin, in the same manner as common winds. 

 This, also, may occasion a different order of change in the ob- 

 served winds and weather from that which is commonly noticed 

 in a regular whirlwind storm. 



Owing to such causes, the oscillations of the barometer are of- 

 ten irregular ; and this is particularly noticeable in the higher 

 latitudes. 



7. In most gales of wind there is, probably, a subordinate mo- 

 tion, inclining gradually downward and inward in the circumja- 

 cent air, and in the lower portions of the gale ; and a like degree 

 of motion, spirally upward and outward, in the central and higher 

 portions of the storm. This slight vorticular movement is be- 



