SCIENCE OF COMMON THINGS. 81 



What are hurricanes ? Breadth and velocity of hurricanes. 



the southern hemisphere, it occurs in. the neighborhood 

 of the Mauritius. 



513 Do the hurricanes occur at particular seasons f 



The West Indian occur from August to October / the 

 Mauritian from February to April. 



514 What have recent investigations shown the hurricanes to be? 



Extensive storms of wind, which revolve round an 

 axis either upright or inclined to the horizon ; while 

 at the same time the body of the storm has a progres- 

 sive motion over the surface of the ocean. 



515 Illustrate more clearly the manner in which a hurricane moves f 

 It is the nature of a hurricane to travel round and 



round as well as forward, much as a corkscrew tra- 

 vels through a cork, only the circles are all^^, and de- 

 scribed by a rotatory wind upon the surface of the water. 



516 In ivhat direction would a ship revolving in the circles of a hurri- 

 cane find the wind ? 



As the ship revolved, she w r ould in turn find the 

 wind blowing from every point of the compass. 



517 What is known concerning the distance travelled by hurricanes f 



The distance traversed by these terrible tempests is 

 immense. The great gale of August, 1830, which oc- 

 curred at St. Thomas on the 12th, reached the Banks 

 of Newfoundland on the 19th, having travelled more 

 than three thousand nautical miles in seven days / the 

 track of the Cuba hurricane of 1844: was but little infe- 

 rior in length. 



518 What is known of their progressive and rotary velocity f 



Their progressive velocity is from seventeen to forty 

 miles per hour but distinct from the progressive velo- 

 city is the rotary, which increases from the exterior 

 boundary to the centre 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. 



519 How great is the breadth of the hurricane $ 



The surface simultaneously swept by these tremen- 

 dous whirlwinds is a vast circle varying from one hun- 

 dred to Jive hundred miles in diameter. 



