$6 ESSAYS AND OBSERVATIONS 



2^th query, at the end of his optics, 

 may be urged with equal fnccefs againft 

 this fuppofed aether, " It is of no ufe ; 

 '* and, as there is no evidence for its cx- 

 " iftence, it ought to be reje(5led." 



I mull own, at the fame time, great re- 

 ludance to a dodrine which overturns, 

 or feems to overturn, the mofl: beautiful 

 part of Sir Ifaac's own theory, and that 

 which affords the ftrongeft conviclion of 

 its truth, viz. the connedlion, by a com- 

 mon caufe, betwixt the curvilinear motion 

 pf the planets, and the defcent of bodies 

 towards the center of this earth. Sup- 

 pofing an aetherial medium to be the caufe 

 of the former, it cannot well alfo be the 

 caufe of the latter. Among other reafons, 

 this occurs, that the different denfities of 

 the fuppofed aether, on the oppofite fides 

 of a bit of matter left free in the air, 

 muft be, quam proxime^ nothing : And the 

 confequence is, that the bit of matter in- 

 volved in a medium which preffes equal- 

 ly «K^^^z/ay«<? or ^«(3»2/)r(?x//«/?, will either 

 remain at reft, or move with a very flow 

 pace. But this is contrary to fad ; for 



the 



