Intelligence  and  Miscellaneous  Articles.  473 
versa]  force  near  the  end.  In  going  round  the  magnet  there  are  six 
maxima  and  six  minima  of  force. 
The  law  of  attraction  of  the  core  of  a  galvanic  coil  is  not  very  dif- 
ferent from  that  of  a  magnet. 
The  force  produced  by  the  core  within  the  coil  is  very  much 
greater  than  that  produced  by  the  coil  alone.  In  some  positions 
of  the  small  compass  it  is  about  forty  times  as  great,  and  in  some 
about  1  70  times  as  great. 
The  law  of  force  at  different  parts  of  the  coil  differs  greatly  from 
that  at  corresponding  parts  of  the  magnet  or  core.  In  the  coil  it  is, 
proportionally,  far  greater  at  the  end,  and  its  direction  is  different. 
Near  the  end  of  the  magnet  or  core  the  directions  of  force  converge 
to  a  point  within  it,  distant  from  the  end  by  about  T^  part  of  its 
length.  Near  the  end  of  the  coil,  the  directions  of  force  converge  to 
a  point  as  exactly  as  possible  at  the  centre  of  the  end  of  the  coil. 
The  author  then  describes  the  graphic  process  by  which  he  has 
resolved  the  entire  magnetic  forces  into  constituent  parts  in  the  di- 
rections longitudinal  and  transversal  to  the  magnet,  at  every  station, 
and  gives  tabular  statements  of  the  magnitudes  of  those  constituent 
parts.  A  comparison  is  made  with  the  results  of  an  assumed  law, 
but  no  satisfactory  agreement  is  obtained. 
An  Appendix  is  subjoined,  containing  an  investigation  by  James 
Stuart,  Esq.,  of  the  theoretical  attraction  of  a  galvanic  coil  upon  a 
small  mass  of  magnetism,',  and  a  tabular  comparison  of  the  numerical 
values  obtained  from  this  investigation  with  the  numerical  values 
found  by  experiment.     The  agreement  is  satisfactory. 
"  On  a  mode  of  Measuring  the  Internal  Resistance  of  a  Multiple 
Battery  by  adjusting  the  Galvanometer  to  Zero."  B.  M.  Jules 
Raynaud. 
The  author  points  out  that  the  method  given  by  Mr.  Henry  Mance 
for  this  purpose,  and  described  in  vol.  xix.  of  the  '  Proceedings  of 
the  Royal  Society'  (p.  252)*,  is  identical  with  that  which  he  had 
himself  previously  given,  and  which  is  described  in  the  '  Comptes 
Rendus'  for  July  22,  186/  ;  at  least  the  only  difference  is  that  M. 
Raynaud  prescribes  putting  the  poles  in  connexion  with  the  earth, 
which  of  course  is  not  necessary. 
LX.  Intelligence  and  Miscellaneous  Articles. 
ON  THE  ABSORPTION -SPECTRA  OF  THE  VAPOURS  OP  SELENIUM, 
rROTOCHLORIDE  AND  BROMIDE  OE  SELENIUM,  TELLURIUM, 
PROTOCIILORIDE  AND  PROTOBROMIDE  OF  TELLURIUM,  PROTO- 
BROMIDE  OF  IODINE,  AND  ALIZARINE.       BY  D.  GERNEZ. 
1"  RECENTLY  announced  to  the  Academy f  that  the  property  of 
-*-  giving,  by  interposition,  systems  of  dark  lines  in  continuous  lumi- 
nous spectra,  far  from  being  exhibited  exceptionally  by  a  few  sub- 
stances, is  found  again  in  a  number  of  more  or  less  coloured  vapours, 
in  which  I  have  been  able  to  observe  them  by  operating  on  a  suffi- 
*  Phil.  Mag.  S.  4.  vol.  xli.  p.  318. 
t  Comptes  Rendus,  vol.  bait,  pp.  660  &  803. 
