and  the  Magnetic  Relations  of  the  Heavenly  Bodies.       449 
Generalizing  the  results  we  have  arrived  at,  taking  into  ac- 
count the  general  similarity  in  the  history  of  development  of  all 
the  larger  heavenly  bodies,  we  may  express  this  generalization 
in  the  following  terms  : — 
All  rotating  heavenly  bodies  possess  magnetical  poles  which  do 
not  coincide  exactly  with  the  p>oles  of  rotation.  During  the  gra- 
dual cooling  the  polarity  changes  signs,  so  that  a  glowing  liquid 
body  possesses  the  opposite  polarity  to  that  of  one  which  is  co- 
vered by  a  solid  crust. 
The  magnetic  polarity  disappears  : — first,  when  the  change  of 
signs  takes  place,  i.  e.  in  that  phase  where,  as  in  the  stars  of  va- 
riable brightness,  the  slag-like  masses  have  already  taken  the 
character  of  extended  continents ;  and  secondly,  when  the  nu- 
cleus has  become  entirely  solid. 
After  these  considerations  the  existence  of  a  magnetical  rela- 
tion between  the  planets  and  the  sun  is,  from  the  stand-point 
of  my  theory,  to  be  regarded,  at  least  qualitatively,  as  a  physical 
necessity.  Only  observation  can  give  us  information  as  to  the 
quantitative  conditions.  In  the  following  it  shall  be  investigated 
how  far  the  above  theoretical  considerations  can  account  for  the 
general  character  of  those  relations,  so  far  as  it  can  be  legiti- 
mately deduced  from  the  observations. 
15. 
The  sun's  axis  of  rotation  is,  according  to  the  observations  and 
calculations  of  Sporer,  inclined  at  an  angle  of  6°  57'  to  the  plane 
of  the  ecliptic.  The  longitude  of  the  ascending  node  of  the 
sun's  equator  is  (in  1866*5)  74°  36'.  From  this  the  longitude 
of  the  sun's  north  pole  is  found  to  be  164°  36',  and  that  of  the 
south  pole  344°  36'.  Supposing  a  plane  to  be  laid  through  the 
sun's  axis  perpendicular  to  the  plane  of  the  ecliptic,  the  earth 
in  its  path  round  the  sun  will  cut  this  plane  on  two  days,  on 
September  6  and  March  7.  On  the  first  day  the  sun  turns  its 
north  pole,  on  the  latter  day  its  south  pole,  towards  the  earth. 
It  follows  therefore  that  all  the  effects  produced  on  the  earth's 
surface  by  a  magnetic  induction  of  the  sun  must  have  a  maxi- 
mum at  these  two  times  of  the  year. 
part  of  the  corona  seen  at  total  eclipses  shows  also  this  similarity.  Laraont 
has  drawn  our  attention  to  this  with  regard  to  the  extremely  great  varia- 
bility of  the  protuberances,  which  is  also  observed  in  the  aurora  borealis. 
But  it  must  always  be  borne  in  mind  that  this  analogy  regards  only  a 
certain  class  of  protuberances ;  in  others  the  eruptive  character  of  vol- 
canic phenomena  is  almost  established  beyond  a  doubt.  On  the  classifi- 
cation of  protuberances  into  those  of  cloudy  and  those  of  eruptive  forma- 
tion compare  my  paper  "  On  the  Temperature  and  Physical  Constitution  of 
the  Sun,"  Proceedings  of  the  Royal  Saxon  Society  of  Sciences,  June  2, 
1-70.     Phil.  Mag.  S.  4.  vol.  xl.  p.  313. 
Phil.  Mag.  S.  4.  Vol.  43.  No.  288.  June  1872.  2  G 
