28G WELLS's NATURAL PHILOSOPHY. 



Eecent investio^ations have proved the hur- 



What is the . • n • • i 



nature of the ricaucs to coHsist 01 extcnsive storms ol wind, 



hurricane? i • i i t • • i • i 



which revolve round an axis either upright or 

 inclined to the horizon ; while at the same time the body 

 of the storm has a progressive motion over the surface of 

 the ocean. 



Thus it is the nature of a hurricane to travel round and round as well as 

 forward, much as a corkscrew travels through a cork, only the circles are all 

 flat, and described by a rotary wind upon the surface of the water. A ship 

 revolving in the circles of a hurricane, would find, in successive positions, the 

 wind blowing from every point of the compass.* 



The effect produced by a hurricane upon the atmosphere is very singular. 

 As it consists of a body of air rotating in a vast circle, its center is tlie point 

 of least motion. Mariners who have been caught in such a center, describe tlio 

 unnatural calm that prevails as awful — an apparent lull of the tempest, which 

 seems to have rested only to gather strengtli for greater efforts. The masa 

 of air, however, which constitutes the body of the storm will be driven out- 

 ward from the center toward the margin, just as water in a pail which is 

 made to revolve rapidly flies from the center and swells up the sides. But 

 the pressure of the atmosphere beyond the whirl, checking and resisting the 

 centrifugal force, at length arrests the outward progress of the mass of air, 

 and limits the storm. 



___ , . , The progressive velocity of hurricanes is from seventeen to 



What IS known , ^ 



respecting the forty miles per hour ; but distmct from the progressive velocity 



velocity and jg ^^le rotary velocitv, which increases from the exterior bound- 

 spaces travers- •' - ' 

 ed by hurri- ary to the center of the storm, near which point the force of 



'*°'^® the tempest is greatest, the wind sometimes blowing at the 



rate of one hundred miles per hour. 



The distance traversed by these terrible tempests is also immense. The 

 great gale of August, 1830, which occurred at St. Thomas, in the "West 

 Indies, on the 12th, reached the Banks of Newfoundland on the 19tli, having 

 traveled more than three thousand nautical miles in seven days ; the track of 

 the Cuba hurricane of IS-i-l: was but little inferior in length. 



The surface simultaneously swept by these tremendous whirlwinds is at 

 vast circle varying from one hundred to five hundred miles in diameter. 



Mr. Redfield has estimated the great Cuba hurricane of 1844 to have been 

 not less than eight hundred miles in breadth, and the area over which it pre- 

 vailed during its whole length was computed to be two million four hun- 

 dred thousand square miles — an extent of surface equal to two thirds of 

 that of all Europe. 



• In 184.5, a ship encountered a hurricane near Mauritius. The wind, as the ship 

 Bailed in the circuit of the storm, changed five times completely round in one hugdred 

 and seventeen hours. The whole distance sailed by the vessel was thirteen hundred and 

 seventy-three miles, and at the termination of the storm she was ouly three bundred and 

 fifty-four miles from the place where the storm commenced. 



