( «3 )'

The Geometry of this Figure is most certainly true and Demonstrable.At this I quarrel not; hüt it makes no more in our present diihculry thanif nothing had been laid. For he has made the Circle G F, reprclcnting theEarth, very large in Proportion to the Circle A D ; and then indeed takingrhc point F in the Earths Surfäce, and by Lines from thcncc dividing theAngle A F D into whatever Equal Parts, the intercepted Arches A B, B C,C D, fhall be unequal. But if he had considered, that the Earth is as icwere a point in respect of the Sphere of the fix’d Stars, nay the very An-nual Orbit of the Earth is almost imperceptible, he would have found thatthe Lines FB, FC, FD, must be all conceived as drawn from the point G,and then Equal Angles will intercept Equal Arches, and Equal Arches EqualAngles : and so it happens (at least beyond the polhbility of the disco very ofSense} to the Eye on the Surface of the Earth; so that his drawing his Linesso far from G as F is, and to another Concentrick Circle so nigh as AD, dc-ccived him in this point.

The famous Gajscndus has written four large Epißlcs on this Subject, theSubstancc of all which is, That the Moon being nigh the Horizon, and lookedat through a more foggy Air, casts a weaker Light, and consequently forcesnot the Eye so much as when brighter; and therefore the Pupil does more In-large it solf, thereby transinitting a larger Projection on the Retina. In thisOpinion I find he is not alone, for this Disquisition beingjately revived. by aFrcnch Abbe , he therein follows the Sentiment of Gajscndus, with this addition,That this Contracting and Enlarging of the Pupil causeth a different lhapein the Eye; an open Pupil making the Crystalline stattet, and the Eye longer,and the narrower Pupil shortening the Eye, and making the Crystalline moreConvex: The first attends our looking at Objects whicli are remote, or whichwe think so ; the latter accompanies the viewing Objects nigh at band. Like-wise an open Pupil and stat Crystalline attends Objects of a more Sedate Light,whilst Objects of more forcible Rays require a greater Convexity, and nar-rower Pupil. From tfiele Positions, the Abbe endeavoured to give an Ac-count of our Pkcnomcnon, as follows. When the Moon is nigh the Horizon,by Comparison with interpoled Objects, we are apt to imagine her much sat-tster from us than when more Elevated, and therefore (seys he) we order ouiEyes as for viewing an Object farther from us ; that is, wesomething En-large the Pupil, and thereby make the Crystalline more flat: moreover, theDuskifhnesi of the Moon in that posture does not so much strain the Sight ;and consequently the Pupil will be more large, and the Crystalline more stat:hence a larger Image fhall be projected on the Fund of the Eye, and. there-fore the Moon fhall appear larger. And this Disposition of the Eye thatmag-nifies her, magnifies also the Divisions of our forementioned Lattice, and con-sequently fhe by her Body fhall poste se no more. of the Divisions than whenfhe feems lese. Theso two forementioned Accidents, vß. The Moons imagi-nary Distance and Duskifhness, gradually vanifhing as fhe Rifes, a disterentSpecies is hereby introduced in the Eye, and consequently fhe feems graduallylese and lese, till again fhe approaches nigh the Horizon. These two Opinionso£ Gajscndus and th t.Abbe being so nigh a-kin, I fhall consider them both

together;