8o ESSAYS and observations 



moon, in total ecllpfes, mufi: needs vary like- 

 ways, according to her diftance from the 

 earth at the time of obfervation ; and, if I 

 hiiftake not, be always more inclined to red 

 at entering arid leaving the fhadow,« than irt 

 the middle. Let Aftronomers determine, 

 whether the fhcenomena agree with this 

 theory. It is not furprizing, that this re- 

 fracted light is very faint and obfcure at the 

 diftance of the moon ; -fince its mean denfity 

 there, will be as much lefs than the denfity of 

 the lightof the fetting fun, as the annular fpace 

 of the lower air thro' which it paffes, drawn 

 into the moon's horizontal parallax, is lefs than 

 the area of a great circle of the earth drawn 

 into four times the excefs of the horizontal 

 refradion of the atmofphere above the fame 

 parallax; that is perhaps as i to or more. 

 QuER. XVI. I have obferved, when at fea, 

 that, tho' I prefTed my body and head 

 firmly to a corner of the cabin, fo as to be at 

 feft in refpedl of every objed: about me, the 

 different irregular motions of the fhip, in 

 rolling or pitching, were ftill difcerriible by 

 the fight : How is this fad: to be reconciled 

 to optical principles ? Shall we conclude^ 

 that the eye, by the fudden motions of the 



vefiTel, 



