f 
2 Of Microscopes in General, 
When only one fuch convex Glafs or 
Lens * is ufed for this Intent, the Instru¬ 
ment it is fixt in, however fafhioned, is 
called a Single Microfcope : but if two or 
more Glades are employed, conjointly, to 
magnify O.bjeds more, it is then called a 
Double or Compound Microfcope . 
One remarkable Difference in the EfFed 
of thefe two Inflruments is, that an Objed 
viewed through a Single convex Glafs ap¬ 
pears magnified, in the fame Portion exadly 
as when feen by the naked Eye ; but when 
viewed through a Double Microfcope, com- 
pofed of three con vex Glades, all Parts of it 
become inverted 3 that is, the Top of the 
Objed appears at Bottom, the Right Side on 
the Left, and every Part in the Place mod 
oppodte to its natural and true Podtion : 
The Lights and Shades being alfo inverted, 
the finking Parts appear to rife, and the 
ridng Parts to fink in. 
To what Accident, to what Country, or 
to whom, we are obliged for the Invention 
* The Word Lens properly fign i'iies a fmall Glafs in Figure 
of. a Lentil ; but is extended to any Optic Glafs not very 
chick, which either collects the Rays of Light into a Point 
in their Paifage through it, or difperfes them apart, accord¬ 
ing to the Laws of R.efra£Lon. Jf convex on both Sides, it 
is called a Convex Lens ; but if one Side be flat, a Plano- 
Convex-c if concave on both Sides, it is termed a Concave 
:,en -1 if Hat' on-one Side, a Plano-Concave ; if convex on 
one Side, and concave on the other, a Convexo-Concave , or 
Concavo-Convex » - 
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