356 
ME.  CEACE  CAL^^ET  AXD  ME.  E.  JOHXSOX  OX  THE  EELATITE 
We  shall  refer  to  the  extraordinary  influence  exercised  hy  crystaUization  on  con- 
duction of  heat  when  we  examine  some  of  the  alloys. 
Influence  of  small  amounts  of  imjpu7'ities  on  the  Conducting  Power  of  Metals. 
We  have  thought  that  it  would  be  useful  to  ascertain  the  influence  which  1 per  cent, 
of  a metal  exercises  when  added  to  another,  and  these  are  the  cmious  results  obtained 
with  gold  and  silver : — 
Eoiand.  Conductibility.  Silver  =1000. 
Pure  gold 31-31  981 
Gold  with  1 per  cent,  of  silver  . . . 26-80  840 
Therefore  the  addition  of  1 per  cent,  of  silver,  the  best  conductor,  to  gold,  diminishes 
its  conducting  power  nearly  20  per  cent. 
We  have  observed  much  more  marked  examples  of  the  diminution  of  conductibibw 
of  a metal  by  the  addition  of  1 per  cent,  of  another  metal,  for  example,  whilst  the  con- 
ducting power  of  pure  mercury  is  21-60,  it  is  only  13-15  when  amalgamated  with  1-25  per 
cent,  of  tin.  Professor  W.  Thomson  having  lately  discovered  that  a small  quantity  of 
various  metals  added  to  copper  greatly  modifles  the  conduction  of  electricity  by  this  metal, 
we  deemed  it  advisable  to  try  if  the  conduction  of  heat  by  copper  would  also  be  altered 
if  we  were  to  alloy  it  with  1 per  cent,  of  various  Other  metals.  W^e  were  fortimate 
enough  to  obtain  results  which  coincide  with  his,  namely,  that  some  metals  increase  the 
conduction  of  heat  by  copper,  whilst  others  diminish  it. 
We  have  also  examined  the  influence  which  carbon  exercises  on  the  conductibility  of 
iron,  and  we  hope  that  the  results  observed  will  prove  useful  in  a commercial  point  of 
vdew;  for  as  seen  by  the  flgures  obtained,  the  difierence  is  about  equal  to  18  per  cent. 
The  following  are  the  results : — 
Found. 
Conductibility. 
Silver=1000. 
Malleable  iron  * 
13*92 
436 
Steel  
12*65 
397 
Cast  iron  
11*45 
359 
* The  iron  was  manufactured  from  the  same  cast  iron  as  that  used  in  this  experiment,  and  both  were 
identical  to  those  used  by  Mr.  Joule  in  his  thermo-electrical  experiments.  Their  composition  was  as  fol- 
lows : — 
Analy 
sis  of  cast  iron. 
yVr ought  iron. 
Carbon 
2-275 
0-296 
Silicium 
2-720 
0-120 
Phosphorus 
0-645 
0-139 
Sulphur 
0-301 
0-134 
Manganese  and  aluminium 
traces 
Iron 
94-059 
99-311 
100-000 
100-000 
