on the fpecijic Gravities, &c. of Saline Subjlancts. 207 
for, in the ifirfl place, one Cubic inch of phlogiflicated air 
weighs 0,377 a g ra i n • nGW let us fuppofe, that to this 
phlogiflicated air is added two- thirds of its bulk of phlogiflon ; 
and to make the fuppofitioii hill ftronger, let us alfo fuppofe, 
that phlogiflon has no weight ; then, by the fuppofition, this 
compound of phlogiflicated air and phlogiflon will conflitute 
inflammable air, and amount to a bulk of three Cubic inches, 
and thefe three Cubic inches will weigh no more than 0,377 
of a grain ; but if three Cubic inches of inflammable air weigh 
0,377 a S ra i n > 011e Cubic inch fhould weigh 0,109 of a 
grain, which cannot be ; for then inflammable air would be 
little more than one-third lighter than common air, contrary 
to all the experiments that have been hitherto made, and par- 
ticularly thofe of Mr. cavendish, fontana, and Dr. prtest- 
ley himfelf, which fhew it to be about eleven times lighter 
than common air. Secondly, It is faid, that the matter which 
flamed the glafs black was the true phlogiflic part of inflam- 
mable air, and was afterwards feparated by means of minium. 
This then contained no phlogiflicated air ; but is it not certain, 
that if there had been enough of it, the minium would have 
been reduced and converted into lead ? And might not inflam- 
mable air be again feparated from that lead, though no phlo- 
giflicated or common air were at hand to fupply its other fup- 
pofed conflituent part ? Thirdly, In one of Dr. Priestley’s 
experiments the inflammable air, contained in the glafs tube 
which was mofl heated, was reduced to fo fmall a bubble that 
no experiment could be made on it : therefore, in this, at leafl, 
the quantity of phlogiflicated air did not amount to one-third, 
but was quite inconfiderable ; the remainder then being taken 
up by the calx of lead in the glafs, was pure mere phlogiflon, 
fo that this experiment is a flrong proof of my opinion. 
Fourthly, 
