268 



tvhere four ways meet, is at a full stop, for want of a 

 clear distinction, which of them to take. 



" 6. The greatest astronomers are not agreed, even 

 as to the length of a natural day. 



" Mr. Ferguson observes, 



" The fixed stars appear to go round the earth in 

 twenty-three hours, fifty-six minutes, and four seconds, 

 and the sun in twenty-four hours. Therefore in three 

 hundred and sixty-five days, measured by the returns of 

 the sun to the meridian, there are three hundred and sixty- 

 six days, as measured by the stars returning to it. The 

 former are called solar days, the latter sidereal. But 

 whoever will compare this with the determinations of 

 Dr. Keil, will find them flatly contradictory to each 

 other. And the farther he examines the most celebrated 

 writings, the more deeply lie will be convinced, that 

 neither the precise length of a sidereal day, nor the com- 

 plement of the solar, has yet been determined with cer- 

 tainty/' 



Whoever desires to see these propositions proved at 

 large may have recourse to the book itself. But if these 

 things are so, what becomes of the whole fabric of even 

 Newtonian astronomy ? How can I depend on the calcula- 

 tions of those concerning the motions of the heavens, 

 who know so little about the earth I What instructions 

 can they give me concerning other systems, who are so 

 unskilled with regard to our own ? Why does not some 

 eminent astronomer undertake this daring man, who so 

 violantly attacks the very foundation of their building 1 

 For if his remarks are just, sensible men will be inclined 

 to think, that after all the parade of mathematical de- 

 monstration, there is little more certainty in astronomy 

 itself, than even in jadicical astrology ! 



And how just are the great Mr. Boyle's remarks, upon 

 the whole of natural philosophy ? " The most, says 

 he, even of modern virtuosi, fancy more certainty in 

 their physical theories than a critkal examiner will find* 



