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racy the Abbe 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 common 

 air upon the fpot, but we may with 

 as much eafe alio 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 fpot 

 undergoes itfelf continual changes, 

 we can but very feldom expect an 

 accurate agreement of two experi- 

 ments, uniefs made at the fame 

 time, or uniefs a quantity of the 

 fame air be lhut up in a bottle fuf- 

 ficient for different experiments. 



Until accurate infrruments fit for 

 fuch purpofes are generally known, 

 and employed with all the attention 

 required, we Hi ail not be able to 

 judge of that degree of goodnefs 



which 



