of the common Air at Sea, 365 
many caufes of corruption of various fubftances) ; and 
that the livelinefs we commonly enjoy in frofty weather 
is in a great meafure owing to the fuperior degree of 
purity of our common element at that time. 
I muft now return from this digreffion to the nature 
of the fea air. 
From what I have already related it appears, that the 
difference between the belt atmofpheric air I have yet 
found and the fea air, as I found it by the firft examina- 
tion upon the fpot where chance carried me, is as 9 1 to 
100, the leffer number indicating the beft quality. Now, 
as I found the fea air of fuch a pure quality fo near land, 
I thought it might, with fome degree of probability, be 
expected, that the common air, at a diftance from land, 
would prove of a flill fuperior quality ; for I could fcarce 
believe, that in the firft trial, made without choice of 
place or time, I had juft hit upon a time and a place 
where the fea air is of the firft quality. 
I would have repeated the fame experiment next 
day, November the 4th, when we were in the middle 
of the channel between the Engliflv coaft and Qftend ; 
but the motion of the fhip, which was very great, 
made it impracticable. Not inlirely, however, to 
lofe the opportunity which the voyage afforded me, I 
fdled three phials, made on purpofe for fuch ufe, with 
Vol. LXX. Ccc air, 
