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



changes the wind at both places to north-west, whilst the phe- 

 nomena previously in existence at those stations are removed 

 to others further north. Now it is obvious that whilst at a 

 station C, fig. 4, where the wind is north-east, it may change 

 directly to north-west, at another, E, more to the east, it will 

 change first to south-east if the south wind has the greatest 

 force; but if the north-east become the strongest, which at 

 any particular spot may be the case, the wind in the first part 

 of the storm from south-east may change to north-east before 

 changing to north-west, as shown by some of the data; — a 

 particular instance may be given. 



From the data of the hurricane of 1821 (Law of Storms, 

 p. 17), "At Cape Henlopen, Delaware, the hurricane com- 

 menced at 11| a.m. from E.S.E. ; shifted in twenty minutes 

 to E.N.E. and blew very heavy for nearly an hour. A calm 

 of half an hour succeeded, and the wind then shifted to the 

 W.N.W. and blew, if possible, with still greater violence." 

 " At Cape May, New Jersey" (a little to the north-east of the 

 previous locality), " commenced at N.E. at 2 p.m. and veered 

 to S.E." Thus it appears that at two stations situated with 

 regard to each other as A and E, the phenomena were as 

 follows: — At A the storm arrived at 11^ a.m., and blew as 

 an E.S.E. wind, but about 12 p.m. the north current had in- 

 creased in force and the wind changed to E.N.E., from which 

 point it blew for an hour, or till 1 p.m. All this time it ap- 

 pears there was no storm at E., but the N.E. wind had re- 

 ceded to it at 2 p.m., and began to blow at that time, but the 

 S. wind soon arrived with greater strength and the wind 

 changed to S.E. But if this be the true explanation of the 

 action of these storms, then according to that given of the mode 

 of progression of receding storms, they ought to increase on 

 the western side towards north-west by the recession of the 

 north-east current; and on the south-west towards south-east 

 by the recession of the south wind. Now with regard to the 

 increase on the west side; as the direction of the north wind 

 is opposed to that of the upper current, it is evident that by 

 extending itself to the west, it cannot extend the rarefaction; 

 and this being produced in a direction from south-west to 

 north-east by the flow of the upper current, the resistance on 

 the west side would soon overcome the advance from east : 

 moreover, the north-east wind is not caused simply by its re- 

 cession from south, but by the production or increase of the 

 atmospheric rarefaction, as at E, fig. 1. § 2. None of these 

 causes however operate as obstacles to its increase towards 

 south-east, and hence we find that the storm actually does in- 

 crease towards east, and that throughout its whole extent a 



