364      M.  F.  Zollner  on  the  Origin  of  the  Earth's  Magnetism. 
duced  a  remarkable  law  from  the  observations.  There  is  for 
Europe  a  certain  scale  of  disturbances,  according  to  which,  if  in 
Milan  a  movement  of  10'  takes  place,  the  corresponding  move- 
ment in  Munich  amounts  to  11',  in  Krakau  12',  in  Breda 
16',  in  Gottingen  18',  in  Copenhagen  22',  &c.  According  to 
Bravais,  the  number  of  the  scale  for  Bosskop  would  be  55';  but 
here  the  form  is  already  changed  so  as  almost  to  be  no  longer 
distinguishable." 
The  difference  between  the  two  hemispheres  which  we  have 
deduced  theoretically  is,  of  course,  independent  of  the  cause 
which  produces  the  increase  or  decrease  in  the  magnetic  action, 
whether  this  cause  is  an  inner  one  as  in  the  disturbances,  or  an 
outer  one,  as  this  is  the  case  with  the  influences  the  sun  exerts 
upon  the  earth.  In  accordance  with  this,  Lamont  says  with  re- 
ference to  the  daily  periods  : — 
"  In  the  southern  hemisphere  the  succession  of  the  magnetic 
changes  during  the  twenty-four  hours'  period  is  exactly  the  same, 
but  the  movement  is  throughout  in  the  opposite  direction  ;  where 
a  westerly  movement,  or  an  increase,  takes  place  in  the  north,  an 
easterly  movement,  or  a  decrease,  is  found  in  the  south.  The 
movement  is  smallest  to  the  south  of  the  equator  when  it  is 
greatest  to  the  north,  because  the  winter  of  the  southern  hemi- 
sphere corresponds  to  our  summer."   (L.  c.  p.  268.) 
Finally,  the  following  words  of  Lamont  will  support  materially 
the  views  which  I  have  explained  regarding  the  connexion  be- 
tween the  magnetic  phenomena  on  the  earth  and  the  undulatory 
movement  of  a  subterranean  liquid  mass  : — 
"  However  important  the  magnetic  disturbances  are  for  the 
theory,  they  would  hardly  have  retained  our  attention  so  long,  if 
they  had  not  something  peculiar,  I  might  say  something  magical, 
inasmuch  as  they  are  called  forth  by  invisible  forces,  not  a 
trace  of  which  is  found  to  exist  in  the  other  phenomena  presented 
by  nature." 
"  It  is  even  impossible  to  follow  and  take  down  by  obser- 
vation all  the  small  deviations,  especially  the  wave-like  appear- 
ance which  manifests  itself  in  all  magnetic  changes." 
"  A  uniform  increase  or  decrease  of  the  magnetic  elements 
never  appears;  but  the  change  takes  place  by  starts,  so  that  after 
every  start  a  little  retrograde  movement  is  observed.  We  are  at 
once  reminded  of  the  flux  and  reflux,  where  each  subsequent 
wave  goes  a  little  further  than  the  former  did,  and  between  the 
two  waves  a  backward  movement  of  the  water  takes  place.  The 
magnetic  waves  are  besides  as  little  like  each  other  as  the  waves 
of  the  sea ;  probably  they  will  also  be  different  according  to  the 
geographical  position.  The  passage  of  a  magnetic  wave  in  our 
country  lasts  about  fifteen  seconds.     This  remarkable  peculiarity 
