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Bignefs of the Horizontal Moon at different Times, 
adding alfo the Confideration of the Faintnefs which 
Vapours fometimes throw on the Appearance. 
VI. An Explication of the Experiment made 
in May 1735, as a farther Confirmation 
of what was faid in a Baper given in 
January 30, 1734-5, to account for the 
Appearance of the horizontal Moon feem- 
ing larger than when higher . By the Same . 
H AVING made an Experiment with three Ivory 
Balls for Confirmation of what I had advanced, 
namely, that the Deception arifes from our judging 
the horizontal Moon to be much farther than it is 5 
fome Gentlemen of the Society were convinced by 
the Experiment, but others were not; which obliges 
me to give this further Account of it, that People may 
judge of the Thing in Writing, which could not be 
fo well attended to in the Hurry of feveral Perfons 
viewing the Experiment in Hade. 
1. Two equal Ivory Balls were fet one beyond an- 
other in refped of the Eye at E, namely, A B at 2.0 
Feet Diftance from the Eye, and CD at 40. 
2. It is certain, by the Rules of Optics, that the 
Eye at E or F will fee the Ball C D under an Angle 
but half as big as it fees the Ball A B 5 that is, that the 
Ball C D muft appear no bigger than the Ball o p placed 
by the Side of AB, 
3. But 
