Force  in  the  Contact  of  Metals.  221 
cylinders  insignificant,  which  causes  the  cooling  to  be  propor- 
tional to  the  excess  of  temperature. 
The  passage  of  the  positive  current  from  bismuth  to  copper 
produced  a  cooling  at  the  point  of  union. 
Copper-Tin. 
The  observations  of  the  two  following  experiments  were  mad  e 
at  intervals  of  15  minutes. 
Exp.  36.  Intensity  =  tan  40°. 
Deviations. 
15-18 
14-78 
12-35 
16-73 
17-25 
16-15 
11-08 
Mean 
14-79 
Exp.  37.  Intensity  =  tan  20°. 
Deviations. 
9-60 
5-40 
8-98 
4-18 
3-25 
5-55 
735 
Mean 
6-33 
A  second  series  of  observations  with  the  same  intensity  of  the 
current  as  in  exp.  36,  and  likewise  consisting  of  seven  determi- 
nations, gave  for  the  mean  14*40.  These  two  series  thus  furnish 
the  mean  14-60. 
Calculating  the  results  of  the  above  two  experiments,  we 
obtain  /3y  =  0_,  and  from 
Exp.  36 «,  =  17-40 
„     37 a,=  17-39 
Mean     .     .       17*40 
The  cause  of  the  variations  when  the  observations  take  place 
at  15-minute  intervals  has  been  given  above. 
The  passage  of  the  positive  current  from  tin  to  copper  occa- 
sioned a  cooling  at  the  point  of  union. 
Copper- Silver. 
Exp.  38.   Intensity  of  the  current  =  tan  39°  23'. 
Deviations. 
0-81 
0*69 
0-57 
0-81 
0-86 
Mean 
0-75 
For  an  intensity  of  current  =  tan  45°  we  obtain  a;=0*91* 
The  passage  of  the  positive  current  from  silver  to  copper  pro- 
duced a  cooling  at  the  point  of  contact. 
