354 
That the diamond is a combuftible fub- 
fiance has been long known; but not 
having heard of its beimg burned in at- 
mofpherical, or any other kind of Bite 
had long wifhed to do it; and being fup- 
plred by a friend with two fmall ones, I 
treated them in ae manner, and found 
that near go parts in roo of the air in 
which they were burned was completely 
phlogifticated ; and the quantity not being 
fenfibly changed, the remainder was fixed - 
air, which is an effect fimilar to that of 
heating charcoal of copper in air. The 
diamonds being very imall, and the quan- 
tity of air in which they were burned be- 
ing {mall in proportion, I will not vouch 
for much exaétnefs in the refult. When 
I get Jarger diamonds I will endeavour to 
make the experiment in a more fatisfac- 
tory manner. Both the diamonds weigh- 
ed only 3-r10ths of a grain, and they loft 
in the procefs 15-100 of a grain. The 
air in which they were burned was zths 
of an ounce mea{ure. 
FOSS PRIESTER Y:. 
To the Editor of the Monthh. Megazine. 
SIR, 
PROMISED you another letter on the 
fubject of the phlogiflic thzory, and I 
‘now fend it. You will find it to confit 
of mifcellaneous articles, fome of more 
and others of Jefs importance to the deci- 
fion of the queition that is now beiore the 
public. All the letters that I have fent 
you relate principally to original and re- 
cent experiments, to which I have given 
a good part of the leifure of the lat fum- 
mer, and I do not propoleto do any thing 
more on the fubjecz till I hear from the 
great authors and advocates of the theory 
that I combat in France; 3 and as we have 
Not now any intercourfe with that country, 
it will probably be a confiderable time 
before that can be done. 
IT am glad, however, to find feveral 
able advocates of the fyftem in this coun- 
try; and fome of them, Iam confident, 
will do themfelves honour by their can- 
dour, as well as their ability. I am 
pretty certain, that if due attention be 
given to the fubject, the controverly will 
be decided to general fatisfa€tion in 2 very 
few years. ‘And whenever I fee reafcn 
to think that my opponents have advanced 
all that they can in-anfwer to what I have 
done and Hs itten, I fhall give an account 
of the impreffion that phe obfervations 
fhall have made on my mind, freely ac- 
knowledging any miftakes into whieh I 
may have fallen. 
But with my bel endeavours | to be im- 
2. °. 
Dr. Priefiley on the Doétrine of Phlogiften. 
[*May 
partial, and attentive to every fact that E 
have ftated, I may have overlocked fome 
important eee ances relating to them, 
and have reafoned mceonclufively fre ra them. 
1. I:flammable air is fometimes pre- 
cured when one metal is precipitated by. 
another in its metallic ftate. This is a 
fa& that is very eafily explained on the 
fuppotition that the metal precipitated does 
not require fo much phlogifton as that 
which was diffolved ; whereas the doétrine 
of the decompontion of water cannot, as 
far as E fee, account for the fact, at leaft 
in an eafy and natural way. 
When zinc is ufed to precipitate lead 
from a folution of fugar of lead, inflamma- 
ble air is procured ; “and according to the 
phlogiftic theory ie ought to be fo, fince 
Jead contains much leis phlogifton than 
zinc; fo that when the former is revived 
by means of the latter, it is able to fur- 
nif more than is requifite for the purpofe. 
But if this inflammable air come from 
the decompofition of the water, the oxygen, 
which mutt be developed at the fame time, 
ought to be found either in the water, or in 
what remains of the zine. For it will not 
be pretended to be in the lead that is revived ; 
and there are no other fubfances preient. 
And yet, when I examine this water, I 
find it entirely free from acidity, and that 
it yields air are lefs pure than that of 
the atmofphere. 
Iron, I alfo find, will yield more in- 
flammable air by folution in acids than 
zinc 3 and a faturated {olution of iron in the 
marine acid yields inflammable air by the 
folution of zinc. 
2. In fome of the preceding letters I 
gave an account of the produétion of in- 
lammable air from inc by means of fteam, 
fimilar to that by which the fame kind of 
air is procured from iro. In this cafe 
the iron receives a great addition to its 
weight, which the antiphlogiftians fay, 
arifes from the oxygen correlponding to 
the hy drogen of the indammable air, both 
coming trom the decompofition of the 
water. But as the zinc gains no weight 
in this precefs, the refult of the experi-- 
ment appears to me to be favourable ta 
the phlogiftic th seory, according to which 
the inflammable air comes from the metal. 
This being an experiment of fome con- 
fequence, I have lately repeated it, and it 
- may be worth while to recite fome of the 
particulars of it, Having put an ounce 
of zinc into an earthen tube, to which I 
gave a red heat, I made a fteam pafs over 
it till I had procured about 300 ounce 
meatures of inflammableair ; atter which 
I found the greateft part of the zine re- 
diced 
