352 
ME.  CEACE  CAL\T:ET  AjS^D  ]VIE.  E.  JOHXSOX  OX  THE  EELATITE 
quantity  of  heat  communicated  to  the  bar  in  vessel  B which  was  determined  in  vessel  C. 
but  the  relative  facility  of  conduction  by  various  metals,  all  circumstances  being  the 
same.  The  best  proofs  that  we  can  give  of  the  accuracy  of  the  process  are — 1st,  that 
the  series  of  alloys  which  conduct  heat  in  the  ratio  of  the  equivalents  of  the  metals  com- 
posing them  would  not  have  shown  such  a coincidence  between  the  obseiwed  and  theore- 
tical results  if  our  process  had  presented  any  serious  defects.  2nd,  that  we  have  been 
able  to  determine  with  accuracy  the  marked  influence  exercised  by  the  addition  of  1 per- 
cent. of  a metal  to  another  metal.  3rd,  it  will  be  seen  fui’ther  on  in  the  paper,  that  we 
have  determined  with  precision,  that  in  copper  bars,  haring  different  conducting  surfaces, 
the  observed  result  agrees  with  the  calculated  one. 
The  process  followed  to  ascertain  the  amount  of  heat  absorbed  by  the  vessel  C,  con- 
sisted in  putting  into  the  vessel,  cooled  down  to  the  natural  temperature,  50  cub.  cent, 
of  water,  having  the  temperature  which  the  water  had  when  the  last  experiment  was 
completed,  and  noticing  how  much  heat  was  absorbed  from  the  water  druing  the  quarter- 
hour.  For  example — 
Mean  couductibilitj.  Mean  absorption.  Total. 
Zinc  cast  vertically  . . . 20’03  8-80  28-83 
Antimony  cast  vertically  . 6*12  2-50  8-62 
but  as  20-03  ; 6-12  : : 28-83  : ^=8-80,  the  relative  conducting  power  of  antimony. 
Therefore  it  is  quite  clear  that  the  addition  of  the  heat  absorbed  by  the  vessel  C,  to 
the  heat  of  the  water  in  the  same,  would  have  comphcated  om-  results  without  any 
advantage. 
We  shall  only  give  two  examples  here  to  show  how  very  regrrlarly  the  appar-atirs 
works,  and  how  accurately  it  indicates  the  different  degrees  of  conducting  power  of  two 
metals.  The  increase  of  temperature,  iir  the  sirccessive  five  mirrirtes,  is  in  the  same  ratio 
whether  the  conductors  be  good  or  bad. 
Temperature 
Constant 
Name  of  the  metals. 
Temperature 
of  the  room. 
of  the 
50  cub.  cent,  of 
water  before 
Temperature  of  the  50  cub.  cent, 
of  water  after  each  5 minutes. 
temperature 
of  the 
200  cub.  cent. 
Conductibility 
found. 
Mean. 
beginning. 
of  water. 
Pure  Copper... 
r 20 
1 20 
O 
21 
20 
34.4  4I.7  48°.o 
33-6  41*8  47-1 
0 
90 
90 
27-0  1 
27-1  J 
1 
27-05 
Lead 
r 18 
18'2 
22-0  25-1  27-4 
90 
9-2  1 
9-17  i 
, 
1 
L18 
18*3 
22-1  25-0  27-45 
90 
9-15  j 
In  fact,  it  is  owing  to  the  facility  of  appreciating  within  tv^  o-tenths  of  a degree,  in  twc^ 
successive  essays,  the  conducting  power  of  a metal  or  alloy,  that  we  have  been  able  to 
determine  the  precise  conducting  power  of  so  large  a number  of  alloys  and  amalgams, 
and  even  these  researches  have  required  more  than  a year’s  constant  labour  and  attention. 
The  metals  which  we  used  were  purified  by  the  following-  processes : — 
Gold. — About  140  grammes  of  nearly  pure  gold  were  dissolved  in  aqua  regia,  and  the 
liquid  evaporated  to  dryness.  The  residue  was  dissolved  and  filtered,  and  to  the  filtrate 
