38  The  Magnifying  Power  of  Glasses.
Tbe  FOCAL  DISTANCES
Four  Magnifiers  for  the  Microscope
for  Opake  Objects.
100  Pts.  of  Magnifies
Magnifies  the
an  Inch.
the  Diam.
Superficies,
1.
100
-  10,000
Dist.  of
2.
—  16
F.  Or  30
676
the  Focus -
  at-1o. -
  or  60
3.
—13
160
4.)
1  Inch,
-  8)
-64.
The  magnifying  Power  of  the  Solar  Microscope ¬
  must  be  calculated  in  somewhat  a
different  Manner.  For  hère,  the  Difference
between  the  Focus  of  the  Magnifier,  and
the  Distance  of  the  Screen,  or  Sheet  whereon -
  the  Image  of  an  Object  is  cast,  is  the  Proportion ¬
  of  its  being  magnified.  Suppose,  for
Instance,  the  Lens  made  use  of  has  its  Focus
at  half  an  Inch,  and  the  Screen  be  placed
at  the  Distance  of  five  Feet.  The  Object
will  then  appear  enlarged  in  the  Proportion
of  five  Feet  to  half  an  Inch:  And  as  in  five
Feet  there  are  one  hundred  and  twenty  half
Inches,  the  Diameter  will  be  magnified  one
hundred  and  twenty  times,  which  multiplied ¬
  by  one  hundred  and  twenty,  ſhews  the
Superficies  to  be  magnified  fourteen  thousand ¬
  and  four  hundred  times:  and  by  putting ¬


of