and  the  Magnetic  Relations  of  the  Heavenly  Bodies.        355 
own  measurements  the  curious  influence  of  the  Tyrolese  Alps  on 
the  direction  of  the  magnetic  needle,  an  influence  which  was 
first  found  by  Kreil," 
It  may  therefore  be  of  interest  to  determine  accurately  the 
magnetic  constants  in  places  where  the  deviation  of  the  pen- 
dulum is  observed,  in  order  to  be  able  to  find  out  a  connexion 
between  these  phenomena.  But  such  influences  of  mountain- 
chains  may  possibly  be  explained  by  the  assumption  of  magnetic 
minerals  contained  in  them.  A  treatise  of  Menzzer  lately  pub- 
lished, u  On  the  Connexion  of  the  Configuration  of  the  Conti- 
nents with  the  Situation  of  the  Magnetic  Poles  of  the  Earth,"  is 
of  great  interest  for  this  question.  This  paper  will  be  found  in 
Poggendorff's  Annalen,  supplementary  volume  v.  p.  592,  and  is 
dated  "  Halberstadt,  November  3,  1870."  The  number  of  the 
Annalen  was  published  in  the  beginning  of  August  1871,  and 
came  into  my  hands  on  the  5th  of  August. 
It  is  easily  understood  that  some  indications  given  therein,  as 
well  as  the  results  arrived  at,  must  be  of  the  greatest  interest  for 
my  theory,  which  I  had  already  stated  on  July  25.  In  fact,  we 
may  even  from  some  indefinite  hints  draw  the  conclusion  that 
Dr.  Menzzer  was  conducted  to  quite  similar  views  as  myself  on 
the  origin  of  the  earth's  magnetism. 
So,  for  instance,  at  once  in  the  beginning  of  the  researches  for 
the  foundation  of  the  mathematical  formulae  we  find  the  fol- 
lowing passage : — 
"  We  may  deduce  from  the  earth's  rotation  that  the  positive 
currents  going  round  the  earth  from  east  to  west  are  really  the 
cause  of  its  magnetic  polarity  ;  and  we  may  even  find  the  origin 
of  these  currents.  But  it  is  not  at  present  my  intention  to  give 
this  deduction.  What  I  want  to  show  is  merely  how  we  can 
derive  from  these  currents  in  the  earth  the  situation  of  the  mag- 
netic poles. 
"  If  the  earth  were  covered  throughout  by  a  homogeneous  solid 
crust,  the  currents  connected  with  its  rotation  would  go  round 
the  earth  exactly  from  east  to  west* ;  the  result  would  be  that 
the  magnetic  poles  would  coincide  exactly  with  the  geographical 
poles.  This  is  approximately  the  case  with  that  part  of  the 
earth's  crust  which  reaches  from  below  to  about  half  the  depth 
of  the  sea.  But  the  part  above  consists  of  land  and  sea;  and 
this  circumstance  modifies  the  electrical  currents  in  such  a  man- 
ner that  the  same  tendency  which  appears  in  the  rigid  part  of 
the  earth  as  the  currents  causes  in  the  liquid  part  a  real  back- 
ward movement  of  the  waters. 
*  This  fact  would  not  be  quite  true  according  to  the  above  cause  of  the 
currents ;  for  their  direction  could  only  result  from  an  easterly  and  polar 
component. 
2A2 
