364 
ME,  CEACE  CAEVEET  AND  IHE.  E.  JOHXSOX  OX  THE  EELATIVE 
Found. 
i 
Silver 
= 1000, 
Found. 
Calculated. 
Bar  No,  5.  Copper  =56*12 
Zinc  =43*88 
Bar  No.  6.  Copper  =43*42 
Lead  =56*58 
r 26*8  1 
L 26*9  J 
23*0 
L23*1J 
26*85 
23*05 
23*33 
16*42 
842 
723 
731 
515 
We  wished  to  ascertain  if  the  extent  of  surface  of  the  copper  in  contact  with  the  other 
metal  exercised  any  influence.  We  therefore  had  a bar  made  in  which  there  was  the 
same  relative  weight  of  tin  and  copper,  but  in  which  the  suidace  of  the  two  metals  in  con- 
tact was  only  one  half  of  that  of  the  bar  No.  4.  This  was  effected  by  soldering  together 
one  bar  of  copper,  1 centim.  wide  and  5 millims.  thick,  to  a similar  one  of  tin  (see 
Plate  XXVII.  bar  No.  7)  ; and  although  the  results  leave  some  doubt  whether  the  suidaces 
have  an  action,  still  the  flgures  are  sufliciently  different  to  deserve  serious  consideration. 
Found. 
Mean. 
Calculated. 
Silver = 
= 1000. 
Found. 
Calculated. 
Bar  No.  7 
24*2 
24*15 
20*22 
757 
634 
Bar  No.  4 
24*1 
26*45 
20*22 
829 
634 
The  conductibihty  of  these  bars,  and  especially  of  Nos.  4 and  6,  being  equal  to 
that  of  rolled  copper,  with  which  they  had  been  made,  we  wished  to  see  what  would 
ensue,  if  bars  of  the  same  copper,  and  having  the  same  diameter  or  surface  as  that  of 
the  copper  in  the  above  bars,  were  subjected  to  experiment.  These  are  the  results : — 
Bar  No,  8,  Square  copper  bar  of  7 millims.  square,  or  one  half  the  bulk  of  the  bar 
usually  employed. 
Found. 
Mean, 
Calculated. 
1 
Silver  = 1000. 
Found. 
Calculated. 
19-11 
19-1 J 
19-1 
17-73 
599 
591 
Bar  No.  9*.  Bar  of  rolled  copper,  5 millims.  thick  and  I centim.  wide. 
Found. 
Mean. 
Calculated. 
Silver  = 
= 1000. 
Found. 
Calculated, 
19-4  1 
19-3/ 
19-35 
18-86 
606 
591 
* The  surfaces  in  the  vessels  B and  C of  bar  9 being  to  our  standard  bar  of  copper  5 : 3'5  : : 26'95  : .r=18‘8(). 
