.  Meanwhile,  one  of  the  ablest  French  astron-
omers, Le  Verrier,  experienced  in  computing
perturbations,  was  independently  at  work,  know-
ing nothing  about  Adams.  He  applied  to  his
calculations  every  possible  refinement,  and,  con-
sidering the  novelty  of  the  problem,  his  calcula-
tion was  one  of  the  most  brilliant  in  the  records


The  Dynamical  Period  89

of  astronomy.  In  criticism  it  has  been  said  that
these  were  exhibitions  of  skill  rather  than  helps
to  a  solution  of  the  particular  problem,  and  that,
in  claiming  to  find  the  elements  of  the  orbit
within  certain  limits,  he  was  claiming  what  was,
under  the  circumstances,  impossible,  as  the  result
proved.
In  June,  1846,  Le  Verrier  announced,  in  the
Comptes  Rendus  de  V Academie  des  Sciences,  that
the  longitude  of  the '  disturbing  planet,  for  Jan-
uary ist,  1847,  was  325°,  and  that  the  probable
error  did  not  exceed  10°.
This  result  agreed  so  well  with  Adams's
(within  i°)  that  Airy  urged  Challis  to  apply  the
splendid  Northumberland  equatorial,  at  Cam-
bridge, to  the  search.  Challis,  however,  had
already  prepared  an  exhaustive  plan  of  attack
which  must  in  time  settle  the  point.  His  first
work  was  to  observe,  and  make  a  catalogue,  or
chart,  of  all  stars  near  Adams's  position.
On  August  3ist,  1846,  Le  Verrier  published
the  concluding  part  of  his  labours.
On  September  i8th,  1846,  Le  Verrier  com-
municated his  results  to  the  Astronomers  at
Berlin,  and  asked  them  to  assist  in  searching  for
the  planet.  By  good  luck  Dr.  Bremiker  had  just
completed  a  star-chart  of  the  very  part  of  the
heavens  including  Le  Verrier's  position;  thus
eliminating  all  of  Challis's  preliminary  work.
