13 
)PTIC PRINCIPLES INVOLVED IN MICROSCOPY 
1. Lenses: 
а. Plano-convex. 
б. Biconvex. 
c. Concave. 
d. Biconcave. 
e. Doublets. 
/. Triplets. 
g. Quadruplets. 
2. Objectives: 
a. Achromatics. 
b. Apochromatics. 
c. I’anchromatics. 
3. Oculars: 
a. Huygheniau. 
b. Compensation. 
c. Spectroscopic. 
d. Micrometer: 
e. Projection. 
4. Condensers : 
a. Simple — 
1. Biconvex. 
2. Plano-convex. 
b. Abbe — 
Numerical aperature 1.20. 
Numerical aperature 1.40. 
.5. Microphotography and projection : 
6. Micrometers : 
a. Stage. 
b Ocular. 
c. Projection. 
