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KANSAS CITY REVIEW OF SCIENCE. 



the gyroscope or spinning top. In the figure this would correspond to a motion 

 of the axis NC about the line EC, or, in other words, the pole of the Earth's 

 e(]uator (or the Earth's axis) make a complete revolution about the pole of the 



ecliptic. It requires about 25,000 years for the celestial pole to make this revo- 

 olution. The only effect of one or more planets in conjunction with the Sun 

 would be to increase by an almost infinitesimal amount this attraction. \See 

 Newcomb and Holden's Ast.~\ This motion of the Earth's axis or precession of 

 the equinoxes has been known since the time of Hipparclius. In the time of 

 Hipparchus our present pole star was 12° distant from the pole. The pole has 

 since steadily approached it and will continue to do so till the year 2100, when 

 it will slowly pass by it and at the end of about 12000 years will be near the 

 constellation Lyra. 



Although the direction of the Earth's axis in space is thus constantly chang- 

 ing, yet the position of this axis, relative to the crust of the Earth, remains inva- 

 riable. The idea was advanced many years ago that this motion of precession 

 would result in a change of position of the North Pole on the Earth's surface, so 

 that the northern regions would be covered with ice, as a result of the different 

 direction in which the oceans would be carried by the centrifugal force of the 

 Earth's rotation. Had such a stupendous change taken place in the short space 

 of time allotted by Mr. Blake, it would have been its own messenger of woe, and 

 no prophet or "wise man" would have been needed to announce its arrival. 



It has been shown, however, mathematically, that the position of the poles, 

 and therefore of the equator on the Earth's surface, cannot change except by 

 some variation in the arrangement of the Earth's interior. Scientific investigation 

 has as yet shown nothing to indicate any probability of such a change. 



