524 PROF. JACOBI ON THE APPLICATION OF ELECTRO-MAGNETISM 
of equivalents in galvanic decompositions, it appears that we ought to 
multiply these equivalents by the number of pairs of plates necessary to 
effect the decomposition. This would perhaps be the true measure, for 
after all it is necessary to consume a great number of atoms of zine, in 
order to decompose a single atom of any other substance less decompo- 
sable. In what relates to the difference between quantity and intensity, 
ealoric offers analogies; and in judging of a quantity of gas, we 
ought always to know its volume and its density. I must here quote 
another observation of Mr. Faraday, which is found in the Seventh 
Series, art. 853. He is speaking of a current which is, he says, “ pow- 
erful enough to retain a platina wire 3, of an inch in thickness red 
hot in the air during the whole time” (33 minutes); and he adds in a 
note: “TI have not stated the length of wire used, because I find by ex- 
periment, as would be expected in theory, that it is indifferent. The 
same quantity of electricity which, passed in a given time, can heat an 
inch of platina wire of a certain diameter red hot, can also heat a hun- 
dred, a thousand, or any length of the same wire to the same degree, 
provided the cooling circumstances are the same for every part in both 
cases,” &e. This is quite correct, but we may add that it would be ne- 
cessary to multiply the number of pairs of plates in the same proportion 
with the length of the wire to obtain a current of the same quantity. 
In short in order to heat a wire of 1000 inches to the same degree 
to which a wire of a single inch would be heated by a single pair of 
plates, it is necessary to disengage 1000 quantities of gas, proceeding from 
the same number of pairs. I have thought it right not to suppress this 
remark, considering that in the practical employment of the voltaic 
‘pile ceconomy is requisite. 
16. 
The following is the table of experiments which I have made upon the 
deviation of the needle with relation to the quantity of gas developed 
at the surface of the negative plate of a voltaic pair of plates of silver and 
amalgamated zinc. The specific gravity of the sulphuric acid was 1°25. 
pone ps the easement of cable se ays “ Deaton Sy the gagemen of 1 eobcinch a 
49° 45! 50" 26° 30! 189" 
41° go! B75 24° 59! g17" 
39° 30! 64!65 23° 52! 931" 
34° 45! 39" 93° 7! 246!" 
32° 29! 108!"5 21° 30! 290!" 
99° 144! 20° 15! 319" 
27° 30! 167" 20° 7! 330" 
27° 15! 166" 
The bubbles of air rising regularly enough to serve as a measure, I 
ot are 
