Anal^fts of the Air. i8y 
it again , but could find no difference in 
the fpecifick gravity of the two airs, and it 
was the fame with an air of tartar which 
was lo days old. 
As to the other property of the air, elafli- 
city, I found it exadiy the fame in the air of 
tartar, which was 15 days old, and common 
airi by filling two equal tubes with thefc 
different airs, the tubes were 10 inches long 
and fealed at one end 5 I placed them at 
the fame time in a cylindrical glafs condenf- 
ing receiver, where I compreffed them with 
two additional atmofpheres, taking care to 
fecure myfelf from danger in cafe the glafs 
fhould burft, by placing it in a deep wood- 
en veffel, the water rofc to equal heights in 
both tubes. This receiver was gently an- 
nealed and thereby toughened, by being 
boiled in Urine where it lay till all was 
cold. 
I put alfo into the fame tubes fome new 
made air of tartar, both the tubes ftanding 
in cifterns of waters the air of one of thefe 
tubes I compreffed in the condenfing en- 
gine for fome days, to try whether in that 
compreffed ftate, more of the aifs elafticity 
would be deftroyed by the abforbing va- 
pours 
