[ 4°4 3 
IX, Some Thoughts co cerning the Sun and 
Moon, when near the Horizon, appearing 
larger than when near the Zenith 3 being 
*Part of a Letter from James Logan, 
Lfq , 3 to Sir Hans Sloane, Bart. Brejident 
of the Royal Society, <&c. 
* * * Philadelphia , Sept . 20. 173 5^. 
I T may, perhaps, be needlefs now to add any thing 
in Confirmation of Dr. Wallis's Solution ( fee thefe 
TranfaElions , N° 1S7.) of the San and Moons ap- 
pearing fo much larger at riling or fetting, than 
when in a greater Altitude 5 tho* fome have very 
abfurdly fti'll gone on to account for it from Va- 
pours, which I remember was given me in, my YoUth 
for the true Caufe of it. "Tis true, indeed, that "tis 
thefe Vapours, or the Atmofphere, alone, that make 
thole Bodies, when very near to the Horizon , ap- 
pear in a fpheroidal Form, by refracting, and there- 
by raifing (to Sight), the lower Limb more than the 
upper, yet thefe can be no Caufe of the other. The 
Sun and Moon , each fubtending about half a De- 
gree, appear in the Meridian of the Breadth of eight 
or ten Inches, to fome Eyes more, and to others 
lefsj and in the Horizon to be two or three Foot, 
more or lefs, according to the Extent of Ground 
they are feen over : But if one can have an Oppor- 
tunity, as I have here frequently had, of feeing the 
Sun rife or fet over a fmall Eminence at the Dif- 
tance of a Mile or two with tall Trees on it (land- 
ing 
