Of  MICROSCOPES  in  General.
of  Microſcopes,  is  not  in  me  to  determine:
the  Honour  has  been  given  by  some  to
DREBBEL  a  Dutchman,  by  others  to  FoNTANA ¬
  a  Neapolitan,  and  by,  others  ſtill  to
different  People.  The  first  Appearance  of
them  however  was  about  the  Year  1621;
ſince  when  they  have  been  improving  down
to  the  present  Time.
As  my  Desire  is,  to  make  People  sensible
of  the  Pleasure  and  Information  the  Microſcope ¬
  can  afford,  and  instruct  them  how  to
manage  and  understand  it,  rather  than  how
to.  make  it,  I  ſhall  take  up  none  of  their
Time  with  the  Manner  of  melting,  grinding, ¬
  polishing,  or  setting  of  Glasses;  a  Work
very  few  ot  my  Readers  will  ever  trouble
themselves  about.  But,  instead  thereof,
ſhall  endeavour,  with  all  the  Brevity  and
Clearness  I  am  able,  to  explain  the  Effects
of  Glasses  on  the  Sight,  and  lead  them  gradually ¬
  into  the  Nature,  Uſes,  and  magnifying ¬
  Powers  of  Microscopes.
When  Objects  are  seen  through  a  perfectly
flat  Glaſs,  the  Rays  of  Light  paſs  through
it,  from  them  to  the  Eye,  in  a  ſtrait  Direc
tion,  and  parallel  to  each  other;  and,  consequently, ¬
  the  Objects  appear  very  little  either
diminished,  or  enlarged,  or  nearer,  or  farther
off,  than  to  the  naked  Eye.  But  if  the
Glaſs  they  are  ſeen  through  has  any  Degree
of  Convexity,  the  Rays  of  Light  are  directed ¬
  from  the  Circumference  towards  the
B  2
Center,