different Metals on each other, 269 
He had remarked that feveral metals, fuch as mercury, 
tin, lead, retained their metallic brilliancy as long as they 
were pure, while compounds of them became foon tarnifhed 
and oxydated ; that the mere contaét of two different metals 
feemed to haften their oxydation ; and that, in this manner, 
the mixture employed for foldering the plates of copper 
which cover the obfervatory of Florence, had been {peedily 
changed into a white oxyde at the outer edge of its contaét 
with the copper, &c. He thinks that, in this cafe, the metals 
have a reciprocal aCtion on each other; and that this action, 
more efficacious and more fenfible when the attration of ag- 
gregation of the metals is deftroyed by fufion, exifts no lefs 
between folid metals when they touch each other. 
If the effets, as rapid as thofe of lightning, occafioned on 
the tongue by two metals bronght into conta&, have been 
by fome afcribed to a peculiar fluid not galvanic, or to the 
eleGtric fluid, it is becaufe they did not recolle& that che- 
mical aétion Is exercifed between two bodies with the utmoft 
rapidity. The figns of eleétricity which have been fometimes 
obferyed on feparating two metals in contact, are rather the 
confequences than the caufe of that aétion; for it is known 
that the greater part of chemical operations change the elec- 
tric equilibrium of bodies, and muft confequently give birth 
to electrical phenomena. Without totally excluding elec- 
tricity, therefore, from all ealvante facts, C. Fabbroni thinks” 
that this fluid has fome fhare in the fenfation experienced 
by the tongue from two metals in contaét. This a@tion of 
metals in contact is proved by the following experiment :—~ 
C. Fabbroni put into two glaffes filled une water, pieces 
of different metals, one in each alts. In other glaffes he put 
two pieces of different metals, but kept them from touching 
by interpofine a plate of glafs. In a third feries of glaffes he 
alfo put two pieces of different metals, but in conta&. In 
the metals of the two firft feries he obferved no change, while 
the moft oxydable metals of the third feries were covered with 
an oxyde, which confiderably increafed in the courfe of a few 
days, and the metallic pieces even contracted. a ftrong ad 
herence. The quantity of the caloric which difengages itfelt 
in pthele combuftions is too finall to be meafured, yet the 
light 
