I I P 
a new Eudiometer . 
the fame level when both have the ufual quantity of air in 
them, as otherwife fome errors will arife from the air being; 
more compreffed in one than in the other. This precaution 
indeed does not intirely take away the error, as the level of the 
water in M is not the fame after the airs are mixed as it was 
before ; but in veffels of the fame fize as mine, the error arifing 
from thence can never amount to the 500th part of the whole, 
which is not worth regarding; and indeed if it were much 
greater, it would be of very little confequence, as it would be 
always the fame in trying the fame kind of air. 
There are feveral contrivances which I ule, in order to dimi- 
nifh the trouble of weighing the veffels ; but I omit them, as 
the defcription would take up too much room. 
The veffel A holds 28 2 grains of water, and is the quantity 
which I fhall diftinguifh by the name of one meafure. I have 
three bottles for mixing the airs in, with a meafure B for the 
nitrous air adapted to each. The firft bottle holds three mca- 
fures, and the correfponding meafure i.| ; the fecond bottle- 
holds fix,, and the correfponding meafure 2\ ; and the third 
bottle holds 1 2, and the correlponding meafure 5. The firft 
bottle and meafure is ufed in. trying common air, or air not 
better than that ; the two other in trying dephlogiflicated air. 
The quantity of refpirable air ufed, as was laid before, is 
always the fame, namely, one meafure ; confequently, in 
trying common air I ufe i| meafures of nitrous air to one of 
common ; and in trying very pure dephlogiflicated air I ufe five 
meafures of nitrous air to one of the dephlogiflicated. I be- 
lieve there is no air fo much dephlogiflicated as to require a 
greater proportion of nitrous than that. The way by which 1 
judge whether the quantity of nitrous air ufed is fufficient, is 
by the bulk of the two airs when mixed ; for if that is not 
Ids- 
