DE.  A.  MATTHIESSEN  ON  THE  THEEMO-ELECTEIC  SEEIES.  371 
Calcium  (pressed  wire) — 4-260 
Iron  (pianoforte  wire  No.  4) — 6-218 
Antimony  (axial) — 6-965 
Antimony  (equatorial) — 9-435 
Red  phosphorus  (from  Professor  Scheotter,  from  the  Collection  of  the 
Heidelberg  Chemical  Laboratory) — 9-600 
Antimony  (purified  as  above,  cast) — 9-871 
An  alloy  of  12  parts  of  bismuth,  1 part  of  tin,  cast — 13-670 
An  alloy  of  2 parts  of  antimony  and  1 part  of  zinc,  cast — 22-700 
Tellurium  (from  M.  Alexander  Loewe  of  Vienna,  purified  by  M.  Holtz- 
AiANN,  cast) —179-80 
Selenium  (from  the  Collection  of  the  Heidelberg  Chemical  Laboratory  . . —290-00 
The  electromotive  power  of  a copper  No.  1,  Argentine  thermo-elements,  whose  solder- 
ing-points had  the  temperatures  7°  and  25°,  was  found  by  Dr.  Wild  to  be  equal  to 
18-4.10®  in  the  standard  given  by  Professor  Weber,  where  the  unit  of  length  is  1 milli- 
metre, the  mass  a milligram,  and  the  time  a second ; and  that  of  the  same  thermo-element, 
where  the  difference  of  temperature  at  the  soldering-points  was  100°  C.,  was  found  equal 
to  1-108  compared  with  that  of  a Daniell’s  element,  the  electromotive  power  of  which 
was  taken  equal  1000*. 
The  above  series  agrees  with  that  found  by  Seebeck,  with  the  exception  of  arsenic, 
which  stands  below  iron  according  to  his  experiments ; this  however  is  easily  explained, 
as  different  sorts  of  iron  give  with  each  other  strong  thermo-electric  currents. 
The  manner  in  which  the  experiments  were  carried  out  is  the  following: — Two 
thermo-elements,  whose  warm  and  cold  soldering-points  had  the  same  temperatures, 
were  compared  with  each  other ; these  formed  a circuit  with  the  coil  of  a galvanometer, 
which  surrounded  a magnet  rod  of  about  a pound  weight,  to  which  was  fastened  a 
piece  of  looking-glass,  thereby  allowing  the  defiections  of  the  magnet  to  be  observed 
at  a distance  by  means  of  a telescope  and  scale,  in  the  same  way  as  observations  are 
made  with  the  magnetometer.  The  commutators  were  brought  into  the  circuit;  the 
one  changed  the  direction  of  the  current  in  the  wire  of  the  multiplier,  and  the  other 
allowed  the  currents  of  the  thermo-elements  either  to  pass  in  a direction  so  that  they 
strengthened,  or  so  that  they  opposed  each  other. 
Out  of  the  four  observed  stationary  deflections  of  the  magnet  which  correspond  with 
the  four  different  possible  positions  of  the  commutators,  the  ratio  of  the  electromotive 
powers  of  the  two  thermo-elements  may  easily  be  calculated ; for  if  s, , Sg  ? ^3  ? ^4  be  the 
four  observed  deflections,  and  if  s,  and  be  the  combination  of  the  two  warm  soldering- 
points  of  the  two  elements,  and  and  Sg  that  of  the  warm  soldering-points  of  the  one 
with  the  cold  one  of  the  other,  that  ratio  is  = 7^^ — 
(S2-S3)-(S,-S4) 
All  the  solderings  of  the  different  metals  were  placed  in  two  cubical  zinc  boxes  (of 
about  6 inches  the  side) ; these  had  double  sides,  the  space  between  them  being  filled 
* Poggexdoeit’s  Annalen,  vol.  ciii.  p.  353. 
