and the feeming Converfion of Water into Air . 4 , r 
any perfon to fufpeft a fallacy in the cafe. In this, therefore, 
I muft have acquiefced, as indeed did all my acquaintance’ 
even thofe who had been the mod incredulous on the fubjeft’ 
after they had themfelves feen the experiments. But I was led 
to the farther profecution of this bufinefs, in confequence of 
having obferved that the purity of the air which I procured de- 
pended u£>on the ftate of that which was immediately conti- 
guous to the earthen retort, or tube, in which I fuppofed the 
converfion to have been made ; and that fome communication 
with the atmofpherejwas neceffary to the production of any 
air, as in the experiment with the digefter, and thofe with the 
clay and the burning lens. And fince pure external air was 
necefiary in order to procure good air, it was concluded by 
feveral of my friends, and efpecially Mr. watt, that the ope- 
ration of the earthen retort was, to tranfmit phlogifton from 
the water contained in the clay to the external air ; and that the 
water, thus dephlogifticated, was capable of being converted 
into refpirable air by the intimate union of the principle of 
heat. 
In order to afeertain what the influence of the external air in 
this cafe really was, I inclofed an earthen retort filled with 
moiftened clay in a large glafs receiver, open at both ends, through 
the upper orifice of which (being narrow) I thruft the neck of 
the retort, luting it fo as to be perfe&ly air-tight ; and placing 
the receiver in a baton ot water, by which the air within was 
cut oft from all communication with the external air, 1 fitted 
to the mouth of the retort a glafs tube, through which I could 
receive whatever was produced in the procefs. In this lituation 
I heated the retort bv means of Mr. parkeu’s excellent burn- 
ing lens, when air was received through the tube communi- 
cating with the infidc of the retort as nfuai ; but at the fame 
Vol. LXXIIT. L 1 1 time 
