XIX.  On  the  Thermo-electric  Series.  By  Augustus  Matthiessen,  Ph.I). 
Communicated  by  Chakles  Wheatstone,  Esq. 
Received  November  20,  1857, — Read  January  14,  1858. 
Being  enabled  by  the  method  described  in  the  Philosophical  Magazine  (February  1857) 
to  obtain  wires  of  the  metals  of  the  alkalies  and  alkaline  earths,  I have  determined  their 
places,  together  with  most  of  those  of  the  other  metals  and  some  alloys,  in  the  thermo- 
electric series.  The  alloys  which  were  experimented  with,  are  those  described  by 
Kollman*  as  ghing  with  other  metals  stronger  thermo-electric  currents  than  those  of 
bismuth  or  antimony  under  the  same  circumstances. 
If  A,  B,  C are  ditferent  metals,  and  (A,  B),  (B,  C),  (C,  A)  the  electromotive  powers  of 
thermo-elements  formed  out  of  each  two  of  these  metals,  whose  alternate  soldering-points 
are  at  tw^o  different  temperatures,  then  (A,  B)-1-(B,  C)  + (C,  A)  = 0,  and  therefore  f 
(A,  B)=a — 5, 
(B,  C)=J-c, 
(C,  A)=c— (Z, 
where  the  values  of  a,  c not  only  depend  on  the  two  temperatures,  but  also  on  the 
nature  of  each  of  the  metals  A,  B,  and  C.  As  the  “ differences”  of  the  same  constitute 
the  electromotive  powers,  the  value  for  any  one  of  these  metals  may  be  put  =0.  If 
the  temperatures  of  the  soldering-points  of  a thermo-element  only  vary  slightly,  the 
electromotive  power  may  be  said  to  be  proportional  to  the  difference  of  the  two  tempe- 
ratures, and  under  the  same  conditions  the  quantities  «,  b,  c are  also  proportional  to 
the  difference  of  the  temperatures,  and  their  ratios  to  each  other  therefore  independent 
of  the  same.  If  now  the  value  of  a second  metal  relative  to  the  above-named  value  of 
the  first  be  taken  =1,  the  values  of  the  others  in  relation  to  these  can  be  deduced,  and 
only  depend  on  the  nature  of  each  metal.  These  values  I will  call  the  Thermo-electric 
Numbers  of  the  metals. 
The  results  obtained  are  given  in  Table  I.,  where  the  thermo-electric  number  of 
chemically  pure  silver  is  taken  =0,  and  that  of  a certain  commercial  sort  of  copper  =1. 
Table  I. 
Bismuth  (commercial,  pressed  wire) ff-  35’81 
Bismuth  (pure,  pressed  ware) + 32'91 
Alloy  of  32  parts  of  bismuth  and  1 part  of  antimony  (cast) -k  29‘06 
Bismuth  (pure,  cast) -k24-96 
* Poggendoefjt’s  Annalen,  Ixxxiii.  p.  77  ; Ixxxiv.  p.  75  ; Ixxxix.  p 90. 
t Gehlee,  Physikaliscbes  Worterbuch,  B.  9.  Ab.  1.  S.  776. 
3 D 2 
