. Modern microscopy; a handbook for beginners and students, combining. Microscopy. 104 Modern Microscopy denser on the under side, and the Abbe chromatic and achromatic condensers referred to previously are par- ticularly suitable for this arrangement. The Bull's-eye Condenser. I Many objects, being opaque, cannot be viewed by light from beneath, and consequently have to be illuminated from above. In order to do this Oa bull's-eye condenser is neces- sary. This usually consists of a plano-convex lens mounted on a stand, as shown in the figure. This has a ball and socket joint and a sliding tel
. Modern microscopy; a handbook for beginners and students, combining. Microscopy. 104 Modern Microscopy denser on the under side, and the Abbe chromatic and achromatic condensers referred to previously are par- ticularly suitable for this arrangement. The Bull's-eye Condenser. I Many objects, being opaque, cannot be viewed by light from beneath, and consequently have to be illuminated from above. In order to do this Oa bull's-eye condenser is neces- sary. This usually consists of a plano-convex lens mounted on a stand, as shown in the figure. This has a ball and socket joint and a sliding telescopic tube, by means of which the lens can be placed in any desired position. The plane side of the lens should be turned towards the object, and the convex towards the source of the illumination, whether it be daylight or artificial by lamp. Latterly Mr. Nelson has sug- gested improvements in the con- struction of bull's-eye condensers in order to reduce the large amount of spherical aberration which is a necessary accompani- ment of the single lens. His improved form consists of either two or three lenses in combina- tion, and the advantage obtained, especially in photography, is well worth the additional outlay. The bull's-eye condenser is often of use in conjunction with the sub-stage condenser, to enable the field to be evenly illumin- ated with the latter, as mentioned on page. 96. It will be. Fig. 38.—Stand Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Cross, M. I; Cole, Martin J. Chicago, W. T. Keener & Co.
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