Force  in  the  Contact  of  Metals. 
215 
Exp. 6.  Intensity  =  tan 27c 
Deviations. 
4-11 
100-9    54-35 
11-61 
98-3    59-60 
10'. 
30-3 
41'o 
Exp.  7.  Intensity  =  tan  10 
Deviations. 
11-9 
23-85 
0  0/ 
38-0 
7-5 
24-3 
34-5 
22-65    Mean  23- 65 
Submitting  these  two  experiments  to  the  calculation  above 
indicated,  we  obtain  /3  =  1*625,  and  a= 133*4. 
Now,  taking  the  mean  of  the  four  values  of  a  obtained,  the 
final  result  is  a  =]  32*73.  Thus  at  a  current-intensity  =  1 
=  tan  45°,  there  is  developed  or  absorbed,  at  the  surface  of  con- 
tact between  copper  and  iron,  a  quantity  of  heat  represented,  in 
the  units  chosen,  by  the  number  132*73. 
In  the  following  three  experiments  the  current  was  reversed 
at  the  end  of  15  minutes,  consequently  before  the  temperature 
had  had  time  to  become  stationary.  In  order  to  abridge,  for  all 
the  subsequent  experiments  we  will  only  give  the  reduced 
numbers. 
:p.  8.  Intensity  =  tan  28°. 
Deviations. 
36-35 
36-00 
35-00 
35-93 
Exp.  9.  Intensity  =  tan  10° 
Deviations. 
15*43 
15-20 
14-63 
15-38 
Mean  .  .  35-82 
Mean  .  .  15*16 
Exp.  10.  Intensity  =  tan  18°. 
Devi 
2< 
2' 
2{ 
ations. 
5-78 
H8 
1*45 
5-90 
Mean 
24-08 
Calculating  from  these  numbers  at  and  ftp  corresponding  to 
a  and  ft  of  the  other  experiments,  we  obtain,  for  the  mean  value, 
ft,= 3-1644,  and, 
from  the  observations  with  tan  28°, 
1  QO 
))  ))  ))  xo  i 
Mean     , 
«y  =  92-74 
«y=85-60 
*y=90-ll 
.     89-48 
