[ 383  ] 
XX.  On  the  Electric  Conducting  Power  of  the  Metals.  By  Augustus  Matthiessen,  Ph.D. 
Communicated  by  Charles  Wheatstone,  Esq.,  F.B.S. 
Eeceived  November  20,  1857, — Eead  January  14,  1858. 
Eequiring  for  my  research  on  thermo-electricity  a great  many  metals,  which  were  for 
the  most  part  chemically  pure,  I thought  it  would  be  interesting  to  determine  at  the 
same  time  their  electiic  conducting  power.  The  method  used  for  these  determinations 
was  the  same  as  that  described  in  the  Philosophical  Magazine  (February  1857),  and  the 
experiments  were  made  in  the  Heidelberg  Physical  Laboratory  under  the  direction  of 
Professor  Kiechhoef. 
The  values  given  in  the  following  series  are  the  results  obtained  with  different  wires 
of  the  same  metal  compared  with  silver,  100  at  0°. 
Silver 
Copper,  No.  3 . 
Copper,  No.  2 . 
Gold .... 
Sodium 
Conduct-  Temperature.  Mean  of  Temperature, 
ing  power.  conducting  power. 
. 100  at  0 
100 
0 
. 77-43  at  18-8 
77-43 
18-8 
/ 72-70  at  22-6] 
I 71-43  at  22-6 J 
1 . . 72-06 
22-6 
r 55-16  at  21-61 
.}  55-24  at  21-8 
^ . . 55-19 
21-8 
[ 55-17  at  22-Oj 
1 
. . . 37-43 
21-7 
r 33-44  at  19-21 
Aluminium.  . .<  33-75  at  19-4 1 . . 33-76  19-6 
[ 34-09  at  20-oJ 
Copper,  No.  1 . 
30-36  at  24-0 
30-70  at  24-0  _ 
30-55  at  24-2  ‘ 
. 30-90  at  24-5. 
r 27-41  at  17-41 
30-63 
24-2 
Zinc 
27-42 
at 
17-6 
^ . . 27-39 
17-6 
1 
[ 27-34 
at 
17-8J 
1 
Magnesium  . 
. . . 25-47 
17-0 
Calcium  . 
. . . 22-14 
16-8 
1 
1 22-05 
at 
18-81 
1 
Cadmium  . . .< 
' 22-09 
at 
18-8 
> . . 22-10 
18-8 
22-16  at  18-8) 
3 F 
.MDCCCLVIII. 
