CAUSE OF THE SUN's MOTION. 41 



to absolute zero, there could be no motion of the 

 heavenly bodies. 



Moreover if it be true that there is an unceas- 

 ing circulation of aethereal matter throughout the 

 solar system, it will account for the revolution of 

 the sun on his axis ; a phenomenon which has 

 never yet been explained in accordance with the 

 Newtonian theory ; and the knowledge of which 

 is of fundamental importance to a right under- 

 standing of physical astronomy ; as it is in the 

 laws which regulate the actions of the sun, that 

 we must seek for the origin of planetary motion. 

 For example, it will be shewn hereafter, that the 

 tendency of caloric to unite with other bodies, is 

 in proportion to the quantity of matter they con- 

 tain, ceteris paribus. Hence it is that two pounds 

 of water will condense just twice as much steam 

 as one pound ; and that a small fire is quenched 

 by a large quantity of coal, with which the 

 caloric unites, and thus arrests the process of 

 combustion. We are therefore authorised to 

 infer, that the aggregate force by which the 

 aether of space tends to unite with the different 

 bodies of the solar system, is in proportion to their 

 mass, and inversely as the squares of the dis- 

 tance.* 



* By glancing over the Tables, p. 32, it will be observed that 

 the velocity of planets round the sun does not depend upon their 

 magnitudes, but on their distance from him, and that the same 

 law applies to their satellites ; which accords with the discovery 



