452     M.  F.  Zollner  on  the  Origin  of  the  Earth's  Magnetism, 
16. 
In  order  to  allow  the  reader  to  use  his  own  judgment  as  to 
how  far  the  phenomena  flowing  theoretically  from  a  periodic 
change  in  the  sun's  magnetism  agree  with  the  facts  observed  on 
the  earth's  surface,  I  shall  take  the  liberty  to  communicate 
simply  the  characteristic  passages  of  the  original  papers. 
The  presence  of  a  periodical  decrease  and  increase  in  the 
magnitude  of  the  daily  variations  of  the  magnetic  needle  was 
stated  by  Lamont  already  in  1845*.  In  the  year  ]851  the 
same  philosopher  published  a  paperf  in  which  he  deduced  a  time 
of  10^  years  for  the  duration  of  this  period.  At  the  same  time 
Sabine  {  was  engaged  in  a  research  and  comparison  of  the  dis- 
turbances of  declination  in  Toronto  and  Hobarton  for  the  five 
years  1843-1848,  and  remarked  that  during  this  period  the 
magnitude  and  frequency  of  the  disturbances  increased  from  year 
to  year. 
Sabine  arrived  also  at  the  assumption  of  a  period  in  the  mag- 
nitude of  these  disturbances,  and,  passing  to  the  consideration 
of  a  possible  cause  (/.  c.  p.  121),  says: — 
"As  the  sun  must  be  recognized  as  at  least  the  primary  source 
of  all  magnetic  variations  which  conform  to  a  law  of  local  hours, 
it  seems  not  unreasonable  that  in  the  case  of  other  variations  also, 
whether  of  irregular  occurrence  or  of  longer  period,  we  should 
look  in  the  first  instance  to  any  periodical  variation  by  which  we 
may  learn  that  the  sun  is  affected  to  see  whether  any  coincidence 
of  period  or  epoch  is  traceable.  Now  the  facts  of  the  solar  spots, 
as  they  have  been  recently  made  known  to  us  by  the  assiduous 
and  systematic  labours  of  Schwabe,  present  us  with  phenomena 
which  appear  to  indicate  the  existence  of  some  periodical  affec- 
tion of  an  outer  envelope  (the  photosphere)  of  the  sun ;  and  it  is 
certainly  a  most  striking  coincidence  that  the  period  and  epochs 
of  minima  and  maxima  which  M.  Schwabe  has  assigned  to  the 
variation  of  the  solar  spots  are  absolutely  identical  with  those 
which  have  been  here  assigned  to  the  magnetic  variations." 
Also  at  the  same  time,  and  quite  independently  of  each  other, 
R.  Wolf§  and  Gautier||  had  drawn  attention  to  the  coincidence 
in  the  period  of  sun-spots  with  the  periodical  changes  in  the  earth's 
*  Dove's  Repertorium  der  Physik,  vol.  vii. p.  102.  Compare  also  "Re- 
sults of  the  Magnetical  Observatory  at  Munich,  1843,  1844,  and  1845," 
Abhandl.  d.  II.  Classe  der  bayr.  Acad,  der  Wiss.  vol.  v.  part  1. 
t  Poggendorff's  Annalen,  vol.  lxxxiv.  p.  572. 
X"  Periodical  Laws  discoverable  in  the  mean  effects  of  the  larger  Magnetic 
Disturbances,"  by  Col.  Edw.  Sabine,  R.A.  (received  March  18,  read  May  6, 
1862),  Philosophical  Transactions. 
§  Mittheilungen  der  Berner  naturforschenden  Gesel/schaft,  No.  245. 
Comptes  Rendus,  September  13,  1852.     Astr.  Naclirichten,  No.  820. 
||  Bibliotheque  Vniverselle,  July  and  August  1852. 
