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medium, through which a ray of light paffeth in 
coming from the horizontal Sun, differs from the 
whole quantity of medium, through which another 
ray of light paffeth in coming from the vertical Sun ; 
and the latter experiment being fo confbnant to the 
manner in which the rays of light pafs, through the 
medium of the atmofphere, into the eye ; I therefore 
concluded, that thefe were proofs, that objeds feen 
through a medium of greater depth, or denlity, do 
appear more large ; and that therefore, not only the 
Sun and Moon, but that all other objeds, feen at great 
diftances, under an horizontal diredion, do appear 
larger to the naked eye, than objeds of equal magni- 
tude and diftance do appear, when feen under a ver- 
tical diredion. 
19. Although the quantity of medium, with its 
denfity, be here mentioned, as though it was the effi- 
cient caufe of this effed, poffibly it may be fome 
other caufe in the horizontal vapours, water, and 
other mediums, which produceth effeds nearly pro- 
portionate to the difference ariling from a comparifon 
of the quantity of medium, or denlity. Whether this 
effed arifes from denlity or rarity, refledion, refrac- 
tion, or infledion, acceleration, retardation, or ab- 
forbency of the rays, teems to me to delerve a proper 
enquiry. What others may find to be the caufe of 
thefe phenomena, I cannot determine ; to me it has 
leemed moft natural, that the rays, under the aforegoing 
circumftances, firft become obftruded, and many of 
them wholly abforbed, the reft proceeding with a 
retarded motion, are thereby firft more rededed, and 
then lefs refraded through the humours of the eye ; 
and laftly, the image on the retina becomes hereby 
enlarged. 
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