of Atmospherical Air, Ge. 141 
I come now to the consideration of the last part 
of the publication in question, entitled, «« Conside- 
rations on the Doctrine of Phlogiston and the De- 
composition of Water.”—This part is merely argu- 
mentative. I shall pass over several objections to 
the new theory that have been made and answered 
before, and confine myself to what appears to me 
to be new. 
After stating that mercury, by exposure to the at- 
mosphere in a certain degree of heat, is converted in- 
to the calx, called precipitate per se; which becomes 
running mercury again by exposure to a greater de- 
gree of heat (on which experiment the antiphlogis- 
tians have built their new theory), Dr. Priestley 
says, ‘¢ that all that can be inferred from it is, that, 
in this particular case, the mercury in becoming that 
¢alx imbibed air, without parting with any or very 
little of its phlogiston.” In support of this, he 
mentions, that the calx which remains, after expos- 
ing Turpeth mineral to a red heat, cannot be reviv 
ed completely by any degree of heat; but may be 
revived by substances supposed to contain phlo 
giston. ’ 
It will be recollected that Turpeth mineral is made 
by heating mercury in an equal quantity of sulphuric 
acid till the mixture becomes dry. This sulphate of | 
_ mercury is then washed in warm water, by which 
means a yellow precipitate is obtained, which is the 
Turpeth mineral. When this is again heated, it be~ 
