POWEE  OP  METALS  AUD  ALLOYS  TO  CONDUCT  HEAT. 
368 
These  results  appear  to  us  perfectly  to  substantiate  our  views,  viz.  that  these  alloys 
are  definite  chemical  compounds,  and  not  a mixture  of  metals ; for  if  they  were  the 
latter  they  would  conduct  heat  as  the  bars,  and  would  not  have  a conductibility  of  their 
own.  We  deemed  it  advisable  to  have  a third  bar  made,  in  which  the  cubes  of  copper 
and  tin  alternated,  and  these  are  the  results  obtained  (see  Plate  XXVII.) : — 
Found. 
Mean. 
Calculated. 
Silver 
= 1000. 
Found. 
Calculated. 
Bar  No.  3 | 
18-1  1 
18*3/ 
18-2 
20-22 
570 
634 
The  composition  of  this  bar  is  intermediate  between  that  of  the  alloys  Sn  2Cu  and 
Sn  3Cu,  which  contain  in  100  parts : — 
, 
Obtained. 
Calculated. 
Silver 
= 1000. 
Found. 
Calculated. 
1 equivalent  of  Tin 
2 equivalents  of  Copper 
51-831 
48-17J 
> Conductibility 
13-65 
19-87 
428 
623 
100-00 
1 equivalent  of  Tin 
3 equivalents  of  Copper 
38-21 1 
61-79  J 
> Conductibility 
15-75 
21-37 
494 
670 
100-00 
Whilst  the  bar  is  composed  of — 
Tin 
45-36 
Copper  ... 
54-64 
100-00 
And  conducts  as  a mixture,  or 
18-20 
20-22 
570 
634 
Notwithstanding  these  facts,  we  were  not  prepared  for  the  curious  results  which  we 
obtained  with  the  following  bar,  composed  of  two  longitudinal  bars  of  tin  soldered  to 
two  of  copper  and  placed  in  juxtaposition  (see  Plate  XXVII.  bar  No.  4) ; for  although 
it  contained  in  100  parts  the  same  weight  of  tin  and  copper  as  the  last  bar,  it  con- 
ducted heat  at  quite  a difiFerent  rate ; in  fact,  its  conductibility  was  the  same  as  if  the  bar 
was  entirely  composed  of  pure  copper,  and  did  not  contain  half  its  bulk  of  tin. 
Found. 
Mean. 
Calculated. 
Silver  =1000. 
Found. 
Calculated. 
Bar  No.  4 
26-5  T 
26-4/ 
26-45 
20-22 
829 
634 
These  interesting  results  were  confirmed  by  having  similar  bars  made  of  copper  and 
zinc,  and  copper  and  lead. 
