214 Mr. BowpotN on an all-furrounding Orb. 
In regard to bodies around us, whenever by fight we have 
: been impreffed with certain ideas of colour, form, and magni- 
tude, correfponding to bodies near us, and at an approachable 
. diftance, we have found, by conftant and uniform experience, 
. derived alfo from, and confirmed by, every other fenfe and means 
of information, that fuch bodies do really exift : and having 
thus from experience gained the knowledge, that certain phe- 
nomena do infallibly indicate the exiftence of thofe bodies, the 
phenomena . themifelves do i then alone become the undifputed 
evidence OF that —" 
"Nature is fimple and lbih 1 in its operations; 
‘fame caufe follow like effets ; and thefe indicate the fame caufe. 
Bodies of every kind, through the medium of light, produce 
their refpective i ig and thefe eua i ei E d 
;thofé bodies. - 
From thefe principles we infer the reility of thore terreftrial 
‘bodies, which, by reafon of their fituation and diftance, can 
-only be the objects of fight : and from the fame principles we 
-alfo infer the reality of the heavenly bodies, the planets, and 
fixt flars. If this laft inference Be! jut, is it not equally juft 
to infer, from the fame ‘principles, the reality of the blue cir- 
.cumambient expanfe : that is, that it is a real concave body, 
-encompafting all vifible nature : which is the exa en 
Of the concave furface of the orb above-mentioned, 
.. There is one appearance of the blue expanfe, which may be 
z = ght to militate with the foregoing account of it. 
dni a clear day, it appears of a brighter blue than in the night, 
Re tu ioned Dy the fun’s light reflected to us by the earth’: s at- 
fphere. From. which circamftance it might be fuppofed, 
otha the gk of the phenomenon doth exift-within the atmof- 
phere, 
