12
PREFACE.
than  two  Degrees,  if  sailing  really
upon  Sir  Isaac  Newton's  Earth,  one
ſhould  imagine  himself  to  be  upon
Mr.  Cassinis.  And  how  many  Ships
have  perished  by  smaller  Mistakes?
THERE  is  this  Consideration
further;  That,  till  the  Figure  of  the
Earth  is  determined,  there  is  no
knowing  how  far  theſe  Errors  may
go.  And  in  fact  it  appears  from  our
Measures  that  such  a  Mistake  will  be
still  greater  than,  from  Sir  Iaacs
Table,  it  could  be  known  to  be.
I  say  nothing  of  the  Mistakes  that
must  happen  in  oblique  Courses.  It
is  needleſs  to  make  any  Estimate  of
them  at  present:  Only  it  is  plain  enough ¬
  that  they  would  be  so  much
the  greater  as  the  Course  approached
to  a  Parallelism  with  the  Equator.
THE