Croll  argues  that  the  distribution  of  ocean-currents  is
due  to  the  system  of  winds,  and  in  the  modern  world  the
existing  system  of  winds  is  due  to  those  astronomical
causes  that,  by  help  of  eccentricity  have  produced  a
minor  glacial  epoch  in  part  of  the  southern  hemisphere
at  the  present  day,  and  a  remarkably  mild  one  over
Western  Europe  and  great  part  of  the  north.  This
coincidence  of  winds  and  great  ocean  currents  is  shown
by  Dr.  Croll  in  a  map,  the  most  familiar  of  which  to
us,  being  the  westerly  and  south-westerly  winds  and
currents  of  the  Gulf  Stream,  the  warm  winds  from
which  so  largely  raise  the  average  temperature  of
the  British  Islands  and  the  whole  of  the  western  part  of
Europe.  There  being  nothing  equivalent  to  this  current
running  south  towards  the  great  Antartic  Continent  of
Victoria  Land,  this  circumstance,  taken  in  connection
with  the  fact  that  the  southern  winter  occurs  in  aphelion,
has  produced  in  that  region  a  minor  glacial  epoch,  so
that  in  south  latitudes,  between  about  64°  and  78°,  the


Cause  of  Glacial  Epochs.  379

whole  country  is  nearly  entirely  shrouded  in  glacier-ice,
and  is  altogether  uninhabitable  by  man,  while  in  the
northern  hemisphere,  in  equivalent  latitudes,  there  are
no  parts  of  North  America  and  Europe  totally  un-
inhabited, and  even  the  north  of  Norway  in  summer,
when  the  sun  does  not  set,  is  often  inconveniently
warm,  and  the  traveller  is  troubled  with  clouds  of  mos-
quitoes.
