[ 109 ] 
racy the Abbé Fontana has brought 
this truly great difcovery: — 
We have now in our hands the 
means of judging, not only of the 
degree of goodnefs of the como on 
air upon the {pot, but we may with 
as much eafe alfo judge of the qua- 
lity of the air of any country, by 
| fending the air of it in clofe bottles. 
But as the air upon the fame {pot 
_ undergoes itfelf continual changes, 
_Wwe can but sid feldom tt an 
ree or unless a quantity of the 
fame air be fhut up in a bottle fuf- 
ficient for different experiments. 
» Until accurate inftruments fit for 
fuch purpofes are generally known, 
and employed with all the attention 
required, we fhall not be ables to 
— of that degree’ of 
