j6 MERCURY. [Lesson iv. 



with proper substances, produce light and heat at 

 the planets, and calculating by the theorem above 

 mentioned, it has been concluded, that if the 

 earth were placed in the situation of Mercury, its 

 medium of heat : would be sevca limes more intense 

 than the greatest heat uf our torrid zone is in its 

 present situation. And hence it has been asserted, 

 that if the materials of which Mercury is com- 

 posed were exactly of the same nature as those of 

 the earth, they could not long remain without be- 

 ing either melted into a fluid, and dissipated into 

 vapour, or vitrified. Have we not then, in the 

 formation o this planet, another proof of infinite 

 wisdom ? For, if the world were formed by chance, 

 or, as atheistical writers express it, by the fortui- 

 tous concourse of atoms, whence comes it, that 

 Mercury and the Earth should have the materials 

 of which they are composed, so adjusted and ar- 

 ranged as to make them so well adapted for their 

 respective situations, as we have abundant reason 

 to conclude they are? 



It will be necessary to premise, that, though the 

 motions of the planets are tolerably uniform and 

 regular, yet they are not exactly so :. nor are their 

 orbits, or the tracks in which they describe their 

 periodical motions, strictly circular, but rather 

 elliptical j their bodies are not globes, but sphe- 

 riods, being flatted at the ends of their axes, which 

 are called poles, and more protuberant at their 

 middle parts or equator? : their orbits are not all in 

 the same plane, but are variously inclined to each 

 other. However, as it is foreign from my design 



to 



