THE 
LONDON,  EDINBURGH,  and  DUBLIN 
PHILOSOPHICAL  MAGAZINE 
AND 
JOURNAL  OF  SCIENCE. 
SUPPLEMENT  to  VOL.  XLIII.  FOURTH  SERIES. 
LXI.   On  the  Origin  of  the  Earth's  Magnetism,  and  the  Mag- 
netic  Relations  of  the  Heavenly  Bodies.     By  F.  Zollner. 
[With  a  Plate.! 
[Concluded  from  p.  469.] 
20. 
TF  variations  in  the  solar  radiation  connected  with  the  time  of 
rotation  could  be  shown  to  exist,  this  would,  of  course,  have 
to  be  regarded  as  a  support  of  my  theory.  As,  however,  heat 
does  not  exert  a  polar  influence  at  a  distance,  and  as,  accord- 
ing to  my  theory,  the  poles  of  the  currents  on  the  sun's  surface 
are  the  coldest  parts,  we  ought  to  expect  a  double  minimum  of 
radiation  caused  by  the  nutation  of  the  poles ;  and  the  magnitude 
of  these  minima  would  be  influenced  by  the  season.  As  heat  does 
not  possess  any  polar  properties,  it  would  be  possible  that  the 
temperatures  of  the  two  hemispheres,  and  hence  also  their  cold- 
poles,  have  different  values. 
I  take  the  liberty  to  compare  with  these  speculations  the 
results  of  a  comprehensive  research  by  D'Arrest,  now  Director 
of  the  Observatory  at  Copenhagen,  "  On  the  Unequal  Distri- 
bution of  Heat  on  the  Sun"*.  The  name  of  the  author  is  a 
sufficient  guarantee  of  the  correctness  of  his  conclusions. 
(Pp.  79-81.)  "It  has  been  proved  lately,  as  is  known,  by 
thermoelectric  experiments  of  Secchi  in  Rome,  that  the  sun's 
heating- power  is  different  for  different  heliographic  latitudes. 
The  decrease  of  heat  from  the  sun's  equator  to  the  poles,  which 
is  undoubtedly  indicated  by  the  repeated  observations  communi- 
cated in  the  Comptes  Rendus,  recalls  to  our  minds  the  inequa- 
lities in  the  heating-power,  proved  by  Professor  Nervander  in 
Helsingfors  in  1845,  which  show  themselves  in  different  helio- 
graphic longitudes.     These  inequalities  make  themselves  percep- 
*  Proceedings  of  the  Royal  Saxon  Society  of  Sciences,  July  2,  1853. 
Phil.  Mag.  S.  4.  No.  289.  SuppL  Vol.  43.  2  I 
