152 COSM1CAL ARRANGEMENTS. 



drives another: all the bodies affect each other 

 at a distance, as the magnet affects the needle. 

 The production and regulation of such effects, if 

 attempted by our mechanicians, would require 

 great skill and nicety of adjustment; but our 

 artists have not executed any examples of this 

 sort of machinery, by reference to which we can 

 illustrate the arrangements of the solar system. 



Perhaps the following comparison may serve to 

 explain the kind of adjustments of which we shall 

 have to speak. If there be a wide shallow round 

 basin of smooth marble, and if we take a smooth 

 ball, as a billiard ball or a marble pellet, and 

 throw it along the surface of the inside of the 

 basin, the ball will generally make many revolu- 

 tions round the inside of the bowl, gradually 

 tending to the bottom in its motion. The gradual 

 diminution of the motion, and consequent ten- 

 dency of the ball to the bottom of the bowl, arises 

 from the friction ; and in order to make the motion 

 correspond to that which takes place through the 

 action of a central force, we must suppose this 

 friction to be got rid of. In that case, the ball, 

 once set a going, would run round the basin for 

 ever, describing either a circle, or various kinds 

 of ovals, according to the way in which it was 

 originally thrown ; whether quickly or slowly, and 

 whether more or less obliquely along the surface. 



Such a motion would be capable of the same 

 kind of variety, and the same sort of adjustments, 



