and  the  Magnetic  Relations  of  the  Heavenly  Bodies.       347 
From  the  first  two  of  the  given  properties  of  the  sun  follows, 
as  I  have  shown  elsewhere,  the  development  of  the  general  cir- 
culation of  its  atmosphere,  in  consequence  of  which  the  heated 
masses  of  gas  rise  at  •  the  equator  and  hence  generate  in  the 
lower  parts  of  the  atmosphere  polar  currents,  in  the  upper  parts 
equatorial  currents,  which  generally  flow  without  disturbing 
each  other*.  These  currents  exert  a  double  reaction  on  the 
glowing  liquid  surface,  viz.,  1st,  a  thermal  one,  and,  secondly, 
a  mechanical  one.  In  consequence  of  the  first  of  these  reac- 
tions, the  poles  are  cooled  down  by  the  contact  of  the  descend- 
ing and  relatively  cooler  equatorial  currents ;  in  consequence  of 
the  latter,  currents  are  produced  in  the  liquid  surface  by  friction, 
which  change  the  normal  rotation  of  the  globe  into  one  which 
corresponds  to  the  developed  law  of  rotation.  By  a  closer  exa- 
mination of  the  relative  velocities  of  layers  lying  above  each 
other,  we  come,  as  I  have  shown  elsewhere  (/.  c.  p.  76),  to  the  re- 
markable result  that  within  the  liquid  layer  affected  by  the  at- 
mospheric currents  the  velocity  of  rotation  increases  with  increas- 
ing depth,  so  that  the  layers  lying  deeper  are  in  advance  of  those 
lying  above  them. 
Hence  the  currents  in  the  glowing  liquid  surface  of  the  sun 
are  directed  from  east  to  west  relatively  to  the  inner  nucleus, 
which  rotates  like  a  solid  globe;  and  the  law  of  rotation  is 
only  a  consequence  of  the  retardation  which  the  upper  layers  of 
the  rotating  globe  suffer  by  friction  against  the  polar  currents. 
It  follows,  therefore,  that  to  the  law  according  to  which 
liquid  layers  of  the  sun's  surface  lying  on  the  side  of  each  other 
have  greater  rotation-angles  near  the  equator  than  in  higher 
latitudes,  corresponds  a  similar  law  for  layers  lying  above  each 
other. 
In  fact  the  equatorial  parts  of  the  liquid  solar  surface  are  to 
the  polar  regions  as  the  middle  of  a  river  is  to  the  part  which  is 
near  the  borders.     Also  in  the  vertical  direction  a  similar  differ  - 
presentano  come  assai  concordanti  coi  fenomeni  delle  protuberanze,  e  percid 
sotto  questo  rispetto  meritevoli  di  qualche  considerazione  :  e  perche  in 
parte  almeno  si  aceordano  colle  idee  emesse  da  autorevoli  scienziati,  e  prin- 
eipalmente  dallo  Zollner."    (P.  44.) 
*  I  am  glad  that  the  existence  of  these  currents  has  now  been  proved 
by  the  observations  of  the  position  and  inclination  of  protuberances.  In 
their  under  part  these  eruptions  are  directed  to  lower  latitudes,  in  the 
upper  parts  towards  the  poles.  This  is  proved  by  numerous  observations 
of  Tacchini  in  Palermo.  Professor  Sporer,  according  to  a  private  com- 
munication, has  observed  the  same  phenomenon ;  and  he  also  considers  it 
a  proof  of  the  currents  which  I  had  deduced  theoretically.  Dr.  Vogel,  of 
the  observatory  of  Chamberlain  von  Biilow,  and  Secchi  confirm  the  same 
thing. 
