258 Mr. W. Brown on the Oscillations of the Barometer. 



" In lat. 41° 20', long. 66° 25', < tremendous hurricane ' from 

 N.N.E. on the 18th." 



I cannot refer to the charts given by Col. Reid, because the 

 directions of the wind marked out in them do not indicate the 

 direction in any regular order with regard to the two periods 

 of the storm. 



Now the general order of the phaenomena of the storms (for 

 it is the same in both, the second being selected merely be- 

 cause of the information concerning it being more full than 

 in the first one, apparently on account of its position being 

 more westerly, and therefore including a larger portion of the 

 United States) are as follows: — The storm commences at S.E. 

 or N.E., but in both cases terminates at N.W., excepting in 

 a few instances — principally near the limit of the storm in the 

 north — where the direction of the wind at both the onset and 

 termination of the storm is from N.E. The veering of the 

 wind is sometimes from S.E. to N.E. and then to N.W., but 

 more generally at once from S.E. to N.W. ; and when the 

 onset is from N.E., sometimes from N.E. to S.E., and after- 

 wards to N.W., but more frequently directly from N.E. to 

 N.W. The differences between the storms now under con- 

 sideration, and those to which § 16 specially applies, are, 

 — 1st, that in the former the rarefaction of the atmosphere 

 is much more suddenly produced, on account of the much 

 greater force of the wind, and hence the extent and duration 

 of each continuous portion of the storm is much less than in 

 the latter; thus instead of one wind prevailing at once over 

 a large extent of surface, as from the extreme south to the 

 north of England, and for a long period, an American 

 storm, over the same length of tract, consists of many alter- 

 nate portions, in which the direction of the wind varies, as 

 shown in the account given of its changes, and continues only 

 for a few hours; and, 2ndly, in British advancing storms 

 the collision of the north and south current takes place from 

 the flow of the opposite currents towards a rarefaction pro- 

 duced by a previous storm ; but in American storms the rare- 

 faction in the first instance is occasioned by the recession of 

 the storms from localities where the directions of the atmo- 

 spheric currents are the reverse of those which are now con- 

 cerned in it. Now from the distribution of the arrows in the 

 chart, we perceive that the localities where the wind is S.E. 

 have a constant position with regard to those where it is N.E. ; 

 and if we select any three or four positions in the track of the 

 storm, at the time when the wind at the most southerly one 

 has changed to N.W., the wind at the same instant of time 

 will be blowing according to the directions shown by the ar- 



