[ i&q ] 



fully two meafures of any atmo* 

 fpheric air ; he takes particular 

 care to perform every experiment- 

 in the fame manner, as well in the 

 handling of the initruments, as in 

 the exact time, even to a moment, 

 of making the two airs together, 

 of letting the tube iland by, before 

 he examines the number upon the 

 brafs fcale, &x. 



After the whole operation is n- 

 nifhed, he deduct s the number of 

 the fub-divifions of the whole co- 

 lumn of air remaining in the tube 

 from the number of all the ftuV 

 divifions or parts of both airs which 

 were let up ; and the remit gives 

 exactly the number of parts or fub- 

 divifions which were deftroyed : 

 for inftance, if, after the third mea- 

 fure of nitrous air being let up, the 

 next mark of the tube correfponds 



with 



