NATURAL THEOLOGY. 203 



ed and enlightened ; that is to say, that the bodies 

 which require the benefit of his illumination and heat, 

 are placed in the most favorable position for receiving 

 them. We know of no natural cause why the central 

 body must be luminous. We see the wisdom of the 

 arrangement ; but here our knowledge ends. 



T. But there is more to excite an admiration of 

 the wisdom exhibited in this stupendous part of the 

 fabric of the universe. 



A.. In the revolution of the earth and planets 

 around the sun we behold an example of mechanism 

 on a scale exceeding our imagination ; but still, where- 

 in we perceive manifest contrivance ; as much as in 

 the motion of a watch or the turning of a joint. 

 The planets revolve by means of two forces. The 

 one is the force of attraction which the sun exerts 

 upon them, like that of steel upon a magnet. It is 

 termed the force of gravitation : and if they were to 

 comply with this force only, they would rush to the 

 sun and be consumed. The other force is one which 

 continually impels them to move off from the sun, 

 like a ball from a sling ; and if they had obeyed this 

 force alone, they would long since have withdrawn 

 from their orbits into the depths of infinite space. 

 The whole is perfectly illustrated by the whirling 

 round of a ball fastened to the end of a string. The 

 ball is drawn to the hand by the string ; this is one 

 force ; the motion of the ball impels it to recede from 

 the hand, so that if the string should separate, the 

 ball would fly away. This is the other force. Both 

 acting together, compel the ball to revolve round the 



