MOVEMENTS OF TORNADOES. 239 . 



" In the great basins of the Rocky Mountains, 

 tornadoes will spin rapidly on their axes for a 

 long time, as stationary as a sleeping top." The 

 tornado has then only an axial rotation, like the 

 gyroscope balanced on its standard. If the axis 

 is inclined, it begins an orbital revolution which, 

 in its slowness compared with the velocity of the 

 axial rotation, resembles the gyroscope. 



" While the motion of translation of the whirl- 

 wind may be only ten miles or so an hour, its 

 whirling (axial) velocity is often a hundred miles 

 or more an hour. They also move in opposite 

 directions. Two of them were seen to whirl 

 within fifty yards of each other at one and the 

 same time, and in opposite directions." 



Mr. J. W. Phelps, an eye -witness, describes "a 

 tornado about fifteen feet in diameter, which had 

 several small whirls spinning around on its circum- 

 ference. The whole system together described a 

 circuit of about one hundred yards across. We 

 watched it from where it set out, until it returned 

 to that point again. It might be compared to a 

 sun with attending planets moving around a 

 common centre." 1 



Herschel's theory is " that a periodical return of 

 heavenly bodies to the same place is the great law 

 of astronomy," as before quoted. The tendency 

 of matter " to move in a straight line," asserts 



1 The quotations are from " Observations in the Rocky Mountains," 

 by J. W. Phelps. 1858-59. 



