462     M.  F.  Zollner  on  the  Origin  of  the  Earth's  Magnetism, 
minima  (analogous  to  flux  and  reflux);  the  numbers  deduced  for 
the  different  years  show  a  remarkable  consistency.  On  the  other 
hand,  Sabine  proves  that  the  movements  at  Kew  correspond 
exactly  to  those  at  Hobarton,  with  the  exception  that  in  the  two 
opposite  hemispheres  they  are  in  the  inverse  direction ;  that  is 
to  say,  the  north  end  of  needle  in  the  northern  hemisphere  moves 
as  the  south  end  does  in  the  southern  hemisphere.  The  differ- 
ence in  the  magnitude  of  the  movement  is  easily  explained  if  we 
consider  the  difference  in  horizontal  intensity  at  the  two  places. 
In  Kew  this  intensity  is  3*7,  and  in  Hobarton  4*5  (absolute 
English  units).  Sabine  does  not  make  any  supposition  in  order 
to  explain  the  difference  in  sign,  but  only  remarks  that  "  we  may 
assume  either  a  direct  influence,  i.  e.  an  attraction  of  the  needle 
by  the  moon,  or  an  indirect  influence,  i.  e,  a  magnetization  of 
the  earth's  nucleus  by  the  moon : "  these  are  the  words  of  La- 
mont  referring  to  the  contents  of  another  paper  by  Sabine. 
The  circumstance  which  is  urged  as  not  explained,  that  the 
form  of  the  magnetic  influence  is  different  in  the  two  hemispheres, 
is,  according  to  my  theory,  as  shown  above,  a  physical  necessity. 
I  only  state  these  facts,  which  confirm  that  the  magnetic  influ- 
ence of  the  moon  is  just  as  we  expected  it  to  be  from  our  theory, 
and  will  not  give  any  opinion  whether  the  change  in  the  mag- 
netic constants  which  was  recently  observed  at  the  beginning  of 
the  totality  of  a  solar  eclipse  is  caused  by  the  increased  magnetic 
action  of  sun  and  moon,  or  rather  by  a  mechanical  influence  in 
the  form  of  a  tidal  or  pressure-wave  in  the  glowing  liquid  nucleus 
of  the  earth. 
My  opinion  of  a  mechanical  reaction  on  the  glowing  streams 
in  the  earth  which  accompanies  every  magnetic  induction  and 
the  complication  of  the  phenomena  caused  by  this  will  be  sup- 
ported by  a  theoretical  research  of  Lloyd,  by  which  he  proves 
that  the  influences-of  sun  and  moon  are  rather  caused  by  an  in- 
direct than  by  a  direct  influence  on  the  earth. 
The  paper  bears  the  title*  "  On  the  direct  Magnetic  Influ- 
ence of  a  distant  Luminary  upon  the  Diurnal  Variations  of  the 
Magnetic  Force  at  the  Earth's  Surface.  By  the  Rev.  H. 
Lloyd." 
In  the  introductory  words  the  author  remarks  : — 
"  It  has  been  usual  to  ascribe  the  ordinary  diurnal  variations 
of  the  terrestrial  magnetic  force  to  solar  heat,  either  operating 
directly  upon  the  magnetism  of  the  earth,  or  generating  thermo- 
electric currents  in  the  crust.  The  credit  of  these  hypotheses 
has  been  somewhat  weakened  by  the  discovery  of  a  variation 
which  is  certainly  independent  of  any  such  cause,  namely  the 
lunar  variation  of  the  three  magnetic  elements ;  while  at  the 
*  Phil.  Mag.  S.  4.  vol.  xv.  pp.  193-196  (1858). 
