22t) OBbJiRVATIONS ON THE WINDhj. 



sometimes be an absence of violent wind ; or the violence will pertain to 

 only one of the phases, which the Storm presents, in its regular course 

 over such locality. 



Some Storms are interrupted in their development by the near approach 

 of another Storm. Care must be taken, therefore, not to mistake the N.E. 

 wind of a Storm whose North- Western limb is thus intercepted by a 

 bordering Storm, and which hence is sometimes followed by the natural 

 current of air from the S.W. quarter, for the changes that pertain to the 

 centre of a rotary gale. 



(165.) Velocity. — The velocity or force of the wind in a Cyclonic Storm 

 varies according to the distance from the vortex, being least near the cir- 

 cumference, and greatest near the central calm space, where it has been 

 estimated sometimes to attain a speed of 125 to 150 miles an hour. 



With regard to the rate of progression of the storm-field along its track, 

 the examination of a large number of records has led to the following 

 results. At its origin, and in low latitudes, its average rate of movement 

 is 17 miles an hour, but this is reduced to 10 or 5 miles an hour where the 

 storm recurves in middle latitudes, and here it has even been known to 

 become almost stationary for several days. As it bears off to the East- 

 ward its speed increases to 20 or 30 miles an hour, though Professor 

 Loomis, from his researches, finds they here attain an average speed of 

 only 18 miles an hour. 



From their nature there must necessarily be considerable variation in the 

 course and velocity of these Storms, but the above figures give the average. 



(166.) Indications. — The earliest and surest of all warnings of an 

 approaching Hurricane will be found in that invaluable, and seldom-failing 

 monitor, the Barometer ; the language of which, in the Torrid Zone, is 

 unmistakable, because there it is usually tranquil and undisturbed. When 

 any such warning symptoms are observed, in any quarter of the world, it 

 may be supposed that no time should be lost in making all due prepara- 

 tion, and especially if to such menacing appearances be added the confused 

 and troubled agitation of the sea which often precedes these revolving 

 storms, and always shows that they are at no great distance. But if these 

 combined prognostics should occur within the limits of those regions in 

 which these Cyclones occur, let the seaman immediately consider the pos- 

 sibility, at least, of his being about to encounter a storm of that revolving 

 type of which we have been treating. 



The Barometer will be found an unerring indicator of the approach of 

 these meteors, provided proper attention be paid to its monitions. As a 

 general rule, the following will be its usual vibrations : — Just previous to 

 the commencement of the Hurricane, the mercury will suddenly rise above 

 its normal or ordinary level (see (23) and the accompanying diagrams of 

 Mean Barometric Pressure), accompanied by Anti-Cyclonic winds of some 

 duration, with cool, dry, bracing, and beautiful weather, a clear sky, and 

 very transparent atmosphere.* In a day or two, or sooner, it will begin 

 to fall, and the wind probably rises, showing that the Storm has begun. 



• The Hurricane of September, 1885, was thus indicated at Havana, while it was ye» 

 1,200 miles away. 



