48 c ihe A r e a of ObjeBs. 
Dr. Smith has an Invention akin to this* 
for taking exad Draughts of Objects* view¬ 
ed in Double Microfcopes ; for he advifes 
to get a Lattice made with fmall Silver 
Wires, or fmall Squares drawn upon a plain 
Glafs by the Strokes of a Diamond, and to 
put it into the Place of the Image formed 
by the Objed-Glafs. Then, by transferring 
the Parts of the Objed feen in the Squares 
of the Glafs or Lattice upon iimilar corre- 
fponding Squares drawn on Paper, the Pic¬ 
ture thereof may be exactly taken. 
There are fome other Sorts of Microme¬ 
ters, or Inventions for mealuring the final! 
Objects feen in Microfcopes ; but as they are 
more complex and difficult, I ffiall not fwell 
this Volume with them. 
CHAP. XL 
Of the Area or Portion of an Objed feen. 
HE vifible Area, Field of View, or 
Portion of any Object feen through a 
Microfcope, is in Proportion to the Diameter 
and Area of the Lens made efe of, and it^ 
Power of magnifying, and may be thereby 
determined : dnee, if the Lens is extremely 
fmall, it magnifies a great deal, and, con- 
fequently, a very minute Portion only of an 
Gbjed 
