ASTRONOMICAL HISTORY. 179 



and repaired; (since these exhalations generally fall in a 

 like quantity as they have mounted, and are by no means 

 enough to refresh both the earth and the spheres of heaven, 

 nor by possibility extend to such a height) ; yet notwith 

 standing, though the gross evaporations of the earth stop 

 far short of heaven, if the earth be the &quot; primum frigi- 

 dum&quot; (principle of cold), according to the doctrine of 

 Parmenides and Telesius, it would not be easy or safe for 

 any one to affirm to what height this force, the antago 

 nist and rival of that of heaven, penetrates by a gradual 

 and successive approximation; especially as these sub 

 stances imbibe and propagate to a great distance the na 

 ture and effects of heat and cold. Yet granting that 

 heaven is not affected by earth, that is no objection why 

 the heavenly bodies should not mutually suffer action and 

 change one from another; the sun for instance from the 

 stars, the stars from the sun, the planets from both, all 

 from the interposed ether, particularly that circumambient 

 to the several spheres. Besides, the opinion of the eternity 

 of heaven appears to have derived great force from that 

 mechanism and fabric of heaven, which the astronomers 

 have busied themselves to very little purpose to invent. 

 For they seem to have taken infinite trouble to guard 

 against the opinion that the heavenly bodies suffer any 

 influence but the effect of mere rotation, being in other 

 respects unchangeable and imperturbable. They have 

 therefore nailed up, as it were, the stars in their orbits. 

 And in their several deflections, elevations, depressions, 

 and windings, they have detected as many perfect circles 

 of the just diameter, elaborately paring and smoothing 

 both the convex and concave side of these circles, so that 

 there is found in them no projection or abruptness; but 

 the one being received within the other, and, by reason of 

 its smoothness of curve, placed in exactly the proper con 

 tiguity, yet so as to slide easily into one, move serenely 

 and kindly; which immortal system of impulses easily 

 precludes all agitation and disturbance, the precursors of 

 dissolution. For, doubtless, if bodies so great as are the 

 starry orbs while cutting the ether, do not always con 

 tinually describe the same paths in its expanse, but pass 

 through regions and tracks far removed from one another, 

 sometimes ascending the upper fields of space, sometimes 

 descending towards the earth, sometimes directing them 

 selves to the south, sometimes to the north, there is immi 

 nent danger that numerous impressions, shocks, reactions, 



