106 
Dissecting Lenses. 
^Dissecting Combination Lens, consisting of tinee achro- 
matic lenses (objective) and an achromatic concave eye-piece; 
magnifying 100 diameters with a working distance (9 mm) which 
affords ample room for convenient manipulation with knife and 
needle during observation 
By unscrewing the third and second lens of the objective 
and using the latter without the eye-piece a useful series of 
graduated magnifications may be obtained as shown in the follow- 
ing table: 
o lenses with eye-piece 100 diameters 
without 
(30 
40 
no 
20 
15 
Fig. 56. 
Aplaiiatic Lens after Steiiiheil, witli Haiulle. 
78 Aplanatio Lenses — Steinheil's formula — composed of 
three cemented lenses, giving relatively long focal distances with 
large flat field; the higher lenses for use with the dissecting 
microscopes, the weaker ones as hand lenses or with a lens 
holder. Magnifying 6, 12, 20; in Avood capsule, each .... 12. 
