ASTRONOMICAL HISTORY. 175 



gravity and magnitude, it follows of necessity that nothing 

 is substracted, since there is nothing added to succeed it. 

 Finally, that changeableness which we discover in the 

 outmost portion of the earth seems itself to be only acci 

 dental. For that slight crust of the earth, which appears 

 only to dip a few miles downwards, (within which limits 

 are contained those admirable laboratories and workshops 

 of plants and minerals), would by no means afford so 

 great a variety, much less of such beautiful and high- 

 wrought productions, unless that part of the earth was 

 exposed to action, and ceaseless vellication, from the bodies 

 above. Now if any one think that the warmth and action 

 of the sun and heavenly bodies can transverberate the 

 thickness of the whole earth, such a man may be justly 

 regarded as a superstitious and phrenetic dreamer, since it 

 is clearly seen with how small an impediment they may be 

 refracted and kept out. Thus far of the indissolubility of 

 the earth. Let us now inquire of the changeableness of the 

 heavenly bodies. 



First then, we are not to use this mode of reasoning, 

 namely, that mutations do not take place in heaven, be 

 cause they do not come within our own observation. For 

 remoteness of distance, excess or want of light, and fine 

 ness or minuteness of substance, equally baffle vision : 

 thus, if the eye were placed in the orb of the moon, it 

 could not discern those changes which take place amongst 

 us here on the surface of the earth, such as inundations, 

 earthquakes, structures, or huge masses, which at so great 

 a distance are not equal to the size of a gnat. 



Nor should any one from the circumstance of the inter 

 stellar air of heaven being transparent, and the stars on a 

 clear night appearing of the same number and form, pro 

 nounce too readily, that the entire body of the ether is 

 diaphanous, firm, and immutable. For the atmosphere 

 itself is subject to endless varieties of heat, cold, scents, 

 and every sort of amalgamation with subtler vapours, yet 

 does not therefore lose its pellucid quality: so in like 

 manner we are not to trust to that feature and aspect of 

 heaven. For if those huge masses of clouds which occa 

 sionally cover the heavens, and take from our sight the 

 sun and stars, on account of their nearness to our point of 

 vision, were suspended in the upper part of the atmos 

 phere, they would by no means change the appearance 

 of a serene sky : for neither could they be seen themselves 

 on account of the distance, nor cause any obscuration of 



