422 Dr. pr iest ley’s Experiments relating to Phlogijlon , 
I kept the whole retort in a red heat for feveral hours, and then 
found that, befides lofing thofe three grains, it weighed eight 
grains lefs than it did at firft. 
Before this I had found, that the calcined whiting which I 
had ufed in the firft experiment could not, as fome fuppofed, 
attract from the atmofphere any confiderable part of the air 
which I got from it, after combining water with it : for two 
ounces of the whiting (which was the quantity which I gene- 
rally made ufe of) did not attraCt more than eight grains of 
any thing when it was expofed a whole day in an open difh, 
though it had loft more than half its weight in calcination. 
It has been imagined by fome, that the air which I got in 
thefc earthen retorts was that which had been attracted from 
the atmofphere by the infide furface of them. But, belides 
that no air could ever be produced without water, to obviate 
this objection more particularly, when one of thefe retorts 
was giving its laft portion of air, I immerfed the mouth of it 
in a bafon of water ; and letting it cool in that lituation, filled 
it again without admitting any accefs of air to the infide ; and 
yet, on repeating the procefs with it, the air was produced juft 
as freely as before. This operation I repeated feveral times. 
If it be laid, that the outfide of the retort attracted the air, ftill 
the inlide, being compofed of the fame materials, muft have 
attracted air alfo ; and it would have appeared by the afcent of 
the water from the bafon, the retort being fufficiently imper- 
vious to air. 
By fome it was imagined, that either the air itfelf that I 
procured, or at lead: the power of the retort to contribute to 
the production of it, was owing to fomething that was tranf- 
mitted from the burning coals, but which could not pafs 
through glafs or metals. To determine this, I took an earthen . 
6 tube, 
