18 
OPTIC PRI^XIPLES IXVOLYED IX MICROSCOPY- 
1. Lenses: * 
a. Plano-convex. 
b. Biconvex. 
c. Concave. 
d. Biconcave. 
e. Doublets. 
j. Triplets. 
g. Quadruplets. 
2. Objectives: 
a. Achromatics. 
b. Apochromatics. 
c. Panchromatics. • 
3. Oculars: 
a. Huyghenian. 
b. Compensation. 
c. Spectroscopic. 
d. Micrometer. 
e. Projection. 
4. Condensers: 
a. Simple — 
1. Biconvex. 
2. Plano-convex. 
b. Abbe — 
Xumerical aj^erature 1.20. 
Xumerical aperat-ure 1.40. 
5. Microphotography and projection. 
6. Micrometers: 
a. Stage. 
b. Ocular. 
c. Projection. 
