M.  F.  Zollner  on  the  Origin  of  the  Earth's  Magnetism.     345 
It  may  be  seen,  with  some  difficulty,  by  the  help  of  an  induc- 
tion-coil and  Leyden  jar;  or  even  by  simply  charging  a  Leyden 
jar  with  an  old-fashioned  electrical  machine  and  discharging  it 
in  a  darkened  room.  The  spark  must  be  at  least  an  inch  in 
length  ;  and,  furthermore,  the  size  and  distance  of  the  electrodes 
and  the  charge  of  the  jar  must  be  so  adjusted  that  the  discharge 
shall  be  single — a  condition  not  always  easy  to  fulfil  with  a  short 
striking-distance. 
Hanover,  U.  S.3  February  9,  18/2. 
•XLIV.   On  the  Origin  of  the  Earth's  Magnetism,  and  the  Mag- 
netic Relations  of  the  Heavenly  Bodies.     By  F.  Zollner*. 
1. 
AT  the  last  Meeting  of  the  Royal  Society,  on  the  25th  of 
July,  I  had  already  the  honour  to  communicate  in  broad 
outlines  those  views  by  means  of  wbich  I  derived  from  my 
researches  "  on  the  Law  of  Rotation  of  the  Sun  and  the  large 
Planets  "f,  an  hypothesis  on  the  physical  cause  of  the  earth's 
magnetism,  and  on  its  relation  to  the  phenomena  we  observe  on 
the  sun's  surface.  It  was  then  my  intention  not  to  publish  my 
arguments  before  haviDg  developed  them  in  such  a  manner,  phy- 
sically and  mathematically,  that  I  might  deduce  from  them 
certain  quantitative  consequences  which  may  be  subjected  to  di- 
rect proof  by  observation.  I  was  led  by  the  theoretical  deduc- 
tion of  the  law  of  the  sun's  rotation  to  some  formulae  which 
a°:ree  even  better  with  the  observed  angle  of  rotation  for  different 
heliographic  latitudes  than  the  empirical  formulae  which  have 
been  hitherto  constructed,  and  I  was  therefore  encouraged  to 
subject  my  theory  of  the  earth's  magnetism  to  a  similar  exa- 
mination. 
I  was,  however,  prevented  till  now  by  work  of  different  kind 
from  executing  my  plan  ;  but  as  in  the  mean  time  some  very  in- 
teresting papers  have  appeared,  the  results  of  which  are,  I  think, 
closely  related  to  my  theory,  I  have  decided  to  publish  its  prin- 
ciples already  in  the  following.  I  intend  to  examine  it  afterwards 
more  closely  in  the  manner  mentioned  above  if  this  should  not 
have  been  done  in  the  mean  time  by  others,  which  I  can  only 
desire  in  the  interest  of  the  subject  and  as  a  support  of  my  theory. 
2. 
I  have  tried  in  the  above-mentioned  paper  to  show  that,  ge- 
*  Translated  by  Arthur  Schuster,  from  a  separate  impression,  commu- 
nicated by  the  Author,  from  the  Proceedings  of  the  Royal  Saxon  Society 
of  Sciences,  Oct.  20,  1871. 
t  Proceedings  of  the  Royal  Saxon  Society  of  Sciences,  Feb.  11,  18/1. 
