44B Abbe fontana’s Account of Airs 
air of Iflington is efteemed to be much better. I have 
examined the air of London, taken at different heights; 
(for inftance, in the ftreet, at the fecond floor, and at the 
top of the adjoining houfes) and have found it to be of 
the fame quality. Having taken the air at the iron gal- 
lery of St. Paul’s cupola at the height of 3 1 3 feet above 
the ground, and likewife the air of the ftone gallery 
which is 202 feet below the other ; and having com- 
pared thefe two quantities of air with that of the ftreet 
adjoining; I found, that there was fcarce any fenftble dif- 
ference between them, although taken at fuch different 
heights. 
In this experiment a circumftance is to be confidered, 
which muft have contributed to render the above men- 
tioned differences more fenfible ; this is, the agitation of 
the air of the cupola, for there was felt a pretty brifk 
wind upon it, which I obferved to be ftronger and 
ftronger the higher I afcended ; whereas in the ftreet, and 
indeed in all the ftreets I pafled through, there was no fen- 
fible wind to be felt. This experiment was made at four 
in the afternoon, the weather being clear. The quiclc- 
filver in the barometer at that time was 28,6 inches 
high, and Fahrenheit’s thermometer ftood at 54 0 . 
After having related all thefe circumftances, it will be 
neceffary to give the mean refult of all the various ex- 
periments 
