26 Astronomy and Geology compared. PT. i. 



periodical, but are always the same. The Solar 

 System may be compared to a vast clock, all the 

 wheels and mechanism of which are perfect, and 

 which keeps time with unvarying correctness. In 

 illustration of this proposition, we may select at 

 hazard any one of the parts of this great system, and 

 the result will be the same. 



For example, let us take the Earth's annual revo- 

 lution in its orbit round the Sun. The distance 

 traversed is about 574,310,000 miles, and the velo- 

 city at which the Earth moves in accomplishing this 

 revolution is 65,518 miles an hour, or 18-2 miles 

 per second. Yet this prodigious space is traversed 

 by the Earth every year to a second of time. The 

 difference in the mode of computing the year, 

 whether the sidereal or solar day is adopted, does 

 not in the least affect this argument. The exactness 

 of the Earth's revolution is, in point of time, the 

 same in each. The consequences resulting from 

 this are invariably the same, as is the motion of 

 the Earth itself. For example, the lengthening and 

 the shortening of the days in any given latitude 

 are the same in each succeeding year. The motion 

 of the Earth through its orbit is not less wonder- 

 fully exact when considered with reference to space 



