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PROCEEDINGS OF THE LATE QUARTERLY SITTING 
OF THE NATIONAL INSTITUTE OF FRANCE, - 
Held on the 15th of Meffidor’s or the 5th of July, 1797- 
MeEmorrs IN THE CLASS.OF 
PHYSICS. 
(Concluded from page 201, of the Maga- 
xine for Sepiember.) 
VAVQUELIN has examined, under 
new relations, a{ubftance, neceflary in 
almoft every art. He has fhewn the true 
nature of allum. He has proved that pot- 
afb,.as an ingredient, not only determines 
the cryftallization of that falc, but that 
this alkali enters into its very compofi- 
tion. . He has. made it appear, that the 
fufaie of pot-ath, which is precured 
with fo much facility, may be advan- 
tageoully fubftituted in the fabrication 
of allum to pot-ath itfelf, which is al- 
ways déar, and often impure. He 
teaches fimple- means to correct the bad 
effects of employing certain materials in 
the. cryftallization of the falt of which 
he is treating. He inftructs manufac- 
turers to calculate with more precifion, 
the effects of that compoefition on the 
Bodies with which they mix it; and he 
arrives at this important conclufion, that 
all the minerals, from which allum, 
cryftallized and folid, is extracied through 
the fulfuric acid, contain pot-afh, or al- 
kali, till now denominated vegetable. 
~Kuaproru had announced, that /ex- 
cite, or white. grenat of volcanos, con- 
rained this pot-afh, in the proportion of 
a fifth part. LeLEAVBE has explained 
to the clafs, the ideas of this learned 
German chemift; and Vauquelin has 
farther confirmed his difcovery: he has 
found this fame pot-afh in the lavas 
which contain the white granite; and 
the various labours of Vauquelin hav- 
ing afcertained, beyond all doubt, that 
the alkali, hitherto called vegetable, is 
found in a very confiderable proportion, 
in feveral alluminous minerals in the 
white granite, and in the lavas that con- 
tain this granite; he has thrown a ‘new — 
light, not only on the caufes of thofe 
phenomena which the interior of the 
globe difplays, but alfo on the nature of 
fixed alkalis, and even en that of the 
vegetables, which probably receive, in 
the bofom of the earth, that pot-afh of 
which the origin was only fought after 
in their organs. 
Leucite having conduced to fuch im- 
portant refearches, deferved to be the 
object of particular curiofity. Accord- 
ingly, on the very day that LELIEVRE 
and VAUQUELIN laid down its chemical 
principles before the clafs, it fortunately 
happened, that Havuy unfolded the 
ftructure of this fubftanee, and DoLo- 
MIEU gave its hiftory. 
Havy, by anable application of his the- 
ory has fhewn, that though the cryftals of 
leucite prefent twenty-four furfaces, and 
their natural joints are parallel, fome to the 
fides of a primary folid, and-the others 
to thofe of a fecond; this firnéture, how- 
ever complicated, terminated in a mole- 
cular form very fimple, and required but 
one regular law of: decreafe. ~~ 
Doxtomieu fpoke of the origin of 
leucité, of its nature, its relations, its 
varieties, its fituation in the midft of 
volcanic preduétions, its refiftance to 
fubterraneous fires, and its lying amidft 
fubftances not voleanized. 
Applying, in another Memoir, the 
knowledge of the mimeralogifts eto pro- 
ceffes too little known, he has defcribed 
the art of cutting gun-flints, the nature 
of the filex, or flint-ftone, whence thefe 
flints are extracted, its properties and 
principles, thefe places in France where 
it is found, the manner ‘of its locality 
among other minerals, the inftruments 
ufed in feparating it from them, and the 
operations that reduce it to form. : 
But before we clofé this notice, let us 
inform the. friends of literature, who 
will doubtlefs learn it with pleafure, : 
what a happy concurrence of perfons of 
fcience, diftributed over thofe countries 
the moft enlightened by learning, has 
rendered thefe latter. times memorable 
and precious to the Inftitute. Among 
thofe men, who, in foreign nations, cul-_ 
tivate the field of human knowledge, 
with the greateft fuccefs, whether they 
dwell in the fouthern climates of Europe, 
or inhabit thofe neareft to the Pole— 
whether they contribute to the glory of 
Spain, or ef Denmark, er Sweden— 
whether they add te the literary fplen- . 
dor of Tialy, Switzerland, Germany, or 
Holland, or to that country which pro- 
duced a Franklin, they have: almoft all 
expreffed a readinefs to teitify their ef- 
teem and affeétion for the Inftitute : and 
to its refearches, uniting theirown, have 
tran{mitted to it their ‘recent publica- 
tions, and even their very manutcripts. 
The lift of thofe learned individuals is _ 
too long for infertion here; but the gra- 
; " titude® 
