Mr. cavendish’s Account of a new lLudlometer. 1.07 
remain a little more or a little kfs time before it is fhaken. In 
like manner, if through any fault in the apparatus, the air 
riles in bubbles, as in that cafe it is almoft impoffible to lhake 
the tube loon enough, the diminution is lefs than it ought 
to be. f 
Another great advantage in this manner of mixing is, that 
thereby the mixture receives its full diminution in the Ihort 
time during which it is fhaken, and is not fenfibly altered in 
bulk after that ; whereas, if the airs are buffered to remain 
lbme time in contact before they are lhaken, they will continue 
dirninifhing for many hours. 
The reafon of the abovementioned differences feems to be, 
that in the Abbe Fontana’s method the water is fhaken brilkly 
up and down in the tube while the airs are mixing, wherebv 
each fmall portion of the nitrous air mud; be in contact with 
water, either at the inftant it mixes with the common air, or 
at leaft immediately after ; and it Ihould feem, that when the 
airs are in contaT with water during the mixing, the diminu- 
tion is much greater and more certain than when there is no 
water ready to abforb the nitrous acid produced by the mix- 
ture, This induced me to try whether the diminution would 
not be Hill more certain and regular if one of the two kinds of 
air was added (lowly to the other in fmall bubbles, while the 
veffel containing the latter was kept continually fhaking. I 
was not difappointed in my expectations, as, I think, this me- 
thod is really more accurate than the Abbe fontana’s; and, 
moreover, in the courfe of my experiments I had occahon to 
obferve a circumftance which is neceffary to be attended to by 
thofe who would .examine the purity of air with exactncfs ' by 
any kind of eudiometer, betides toine others which tend very 
P 2 much 
