[ 65 ] 
faturated with fixed air as it admits of, nothing more than 
a repetition of the fame procefs is requifite. In this;' 
account of the apparatus, I have purpofely confined my^ 
felf to the method of uniting fixed air with water; but it 
is to be obferved, that many curious experiments may be 
made with it, both in chemiftry and pharmacy. By its 
afliftance, I have been enabled to imitate very perfe6tly,the 
common mineral waters, and to make aqueous folutions 
of fubftances that were before deemed infoluble in waterr 
Thefe circumftances, however, I fhall referve for a future 
paper, which I fliall have the honour to present to the 
Society, as I have not yet been able to arrange the feve- 
ral fa6ts, which this apparatus has made me acquainted 
with, in the manner I could wifh. 
POSTSCR IPT. 
SINGE the foregoing paper was read, I have con^ 
trived a glafs valve, w^hich feems preferable in fome re- 
fpe6ts to the ivory one therein defcribed. The following 
is a defcription of it. It conlifts of three pieces, as in fig, 
7. The fuperior and inferior pieces are perforated j 
but the middle one is without perforation, having only 
its upper part convex and its under part plane. In fig. 
8. is a perpendicular fedtion of the three pieces com- 
pofing the valve, at the diftance at which they ought to 
be placed, with refpedt to each other, in the tabular part 
of the vefiel (B). This veflel having the glafs valve in 
it, and filled with water, is to be put on the glafs (A), 
VoL. LXV. K con« 
