( 
Mr, Milner on the Production , See , got 
accurately at the time; for the main point I have in view in 
this defeription, is to afeertain the nature of the changes which 
took place ; and thefe do not depend upon the quantities of 
aerial fluids, but upon their properties. Befides, whoever 
(hall repeat thefe experiments will find the relative quantities 
to vary very much, according to the manner of operating ; 
and therefore, for the fake of brevity, I omit to mention 
them entirely. 
3. I began with boiling a little ftrong nitrous acid in a 
fmali retort, the neck of which was clofely luted to one end 
of a gun-barrel. The other end of it was immerfed fome- 
times in water, and fometimes in quickfilver, and eighteen or 
twenty inches of the middle part was furrounded with burn- 
ing charcoal in a proper furnace. In this manner the vapour 
and fumes of the boiling acid were tranfmitted through the 
red-hot tube, and the produce received at the end in the ufual 
manner. 
When the acid was made to boil violently, there paffed over 
a confiderable quantity of undecompofed red nitrous vapour, 
together with a mixture of nitrous and phlogifticated airs. 
When the procefs was conduced more moderately, there 
was lefs nitrous vapour ; and in the mixture of airs which was 
received in the glafs veffels, there was a much greater pro- 
portion of phlogifticated air. 
4. In order to increafe the furface of the red-hot iron, and 
effect a more complete decompofition of the nitrous vapour, 
the gun- barrel was crammed full of iron filings. The experi- 
ments were repeated with great caution, and almoft the whole 
of the produce was found to be phlogifticated air. It is how- 
ever proper to mention, that, notwithftanding every poffible 
care, ftill there will generally be in fome degree an admixture 
Vol. LXXIX. X x of 
