430 



THE PHYSICAL GEOGRAPHY OF THE SEA. 



any one to make any thing of them. Admiral Fitz Boy, in the 

 Meteorological Papers of the Board of Trade, published diagrams 

 of the winds as observed during that storm on board of various 

 vessels in various parts of that sea. I have not been able to rec- 

 oncile them with the cyclone theory. Espy maintains that they 

 confirm his theory ; and his (§ 787) is anti-cyclonic. 



804. The cyclones of the North Atlantic take their rise gener- 

 cvcionos of the North ^^ty (§ '^^5) somewhcrc bctwcen the parallels of 10° 

 ^^^'•^^'^^''- and 20° north. They take a westerly course until 



they fall in with the Gulf Stream, when they turn about and run 

 along upon it until their force is expended. The atmosphere over 

 the Gulf Stream is generally well charged with moisture, and in 

 this fact perhaps will be found the reason why the path of the 

 storm is laid alonsr the Gulf Stream. 



o 



805. The following table is from Birt's Hand- 

 book of Storms: 



Til 3 hurricane sea. 

 son. 



Average Ntimher of Cyclones or Hurricanes which have occurred in different Months 

 of the Year, and in various Regions. 



806. The vortex of a cyclone is often and aptly compared to a 

 c clones in the Missis- nietcor. I havc oftcu obscrvcd the paths of such 

 Pippi vaiky. through the forests of the Mississippi Valley, and 



the path has in no instance that has fallen under my observation 

 been more than a few hundred yards broad. There the track of 

 these tornadoes is called a "wind-road," because they make an 

 avenue through the wood straight along, and as clear of trees as 

 if the old denizens of the forest had been felled with an axe. I 

 have seen trees three or four feet in diameter torn up by the 

 roots, and the top, with its limbs, lying next the hole whence the 

 roots came. Nevertheless, the passage of the meteor, whose nar- 

 row path was marked by devastation, would create a great com- 

 motion in the air, and there would be high winds raging for sev- 

 eral miles on either side of the " wind-road." But (§ 799) let us 

 consider for a moment the effect of the diurnal rotation of the earth 

 upon one of these revolving discs 1000 miles in diameter: its height 



