#66] 
imagined by many, that the indivi- 
dual quantity of the influence ex- 
cited goes the whole round, each 
time contraction is produced. There 
is an experiment, however, first 
(I believe) made by Dr. Fowler, 
which appears to contradict this 
opinion: he brought two differ- 
ent metals into contact with each 
other, in water, at the distance of 
about an inch from the divided end 
of a nerve, placed in the same wa- 
ter, and found that the muscles, 
which depended upon it, were from 
this procedure thrown into con- 
tractions. Now, in this experi- 
ment, there was surely room enough 
for the influence to pass through 
both metals, and the moisture im- 
mediately touching them, without 
going near to the nerve. I think 
it, therefore, probable, that motions 
are in no case produced by any 
thing passing from the dry exciters 
through the muscles and nerve, but 
that they are occasioned by some in- 
fluence, naturally contained inthose 
bodies as moist substances, being 
suddenly put in motion, when the 
two dry exciters are made to touch 
both them ‘and each other ; in like 
manner as persons, it is said, have 
been killed by, the metion of their 
proper quantity of the electric fluid, 
But to return from conjecture to 
' facts, I shall now examine, whether 
it be always necessary to employ 
two dry exciters, that is, two metals 
or one metal and charcoal, in order 
to occasion contractions. 
Gold and zinc, the first the most 
perfect of the metals, the other an 
imperfect one, operate together very 
powerfully in pgoducing contrac- 
tions; while gold and, the next 
most perfect metal, silver operate 
very feebly. It would seem, there- 
fore, that the more similar the me- 
ANNUAL REGISTER, 1798: 
tals are, which are thus used, 
the less is the power arising from 
their combination. Two pieces of 
the same metal, but with different 
portions of alloy, are still more 
feeble than gold and silver; and 
the power of such pieces becomes 
less and less, in proportion as they 
approach each other in point of 
purity. From these facts it has 
been inferred, that, ifany two pieces 
of the same metal were to possess 
precisely the same degree of purity, 
they would, if used together, be en-~ 
tirely inert, in regard to the excites 
ment of muscular contractions ; in 
confirmation of which, many persons 
have asserted, that they have never 
observed muscles to move frem the 
employment of two such pieces of 
metal, or of one piece of metal 
having the same fineness through 
its whole extent. Others, however, 
upon the authority of their observa~ 
tions, have maintained the contrary: 
and to the testimony of these I must 
add my own, as I have frequently 
seen muscular motions produced 
not only by a single metal, but like- 
wise by charcoal alone. Nor will 
credit be denied me on this head, 
after I have pointed out certain 
practices, by which any one of those 
substances may at pleasure be made 
to produce contractions. ‘The most 
proper way of mentioning these 
practices, will, perhaps, be to relate 
in what manner they came to my 
knowledge. 
I one day placed a piece of salver, 
and another of tin-foil, at a small 
distance from each other, upon the 
crural nerve of a frog, and then 
applied a bent silver probe between 
them, with the view of ascertaining, 
whether contractions would arise, 
agreeably to Mr. Volta’sdeclaration, 
from the influence passing through 
& pore 
