. The microscope and microscopical methods. Microscopes; 1896. :oo PI 10 TO-MICROGRA PIIY. [CH. VIII. circle, /. c, the diaphragm of the ocular, is sharp, the resulting picture will not be satisfactor}'. When the diaphragm is sharply focused on the screen, the microscope is focused exactly as though no ocular were present, that is, first with the unaided eye then with the focusing glass ; the object should be in focus in the Fig. 157. Arrangement for Artificial Illumination. f. Lamp with metal chimney, easily made by rolling up some ferrotype plate and making a slit-like opening in
. The microscope and microscopical methods. Microscopes; 1896. :oo PI 10 TO-MICROGRA PIIY. [CH. VIII. circle, /. c, the diaphragm of the ocular, is sharp, the resulting picture will not be satisfactor}'. When the diaphragm is sharply focused on the screen, the microscope is focused exactly as though no ocular were present, that is, first with the unaided eye then with the focusing glass ; the object should be in focus in the Fig. 157. Arrangement for Artificial Illumination. f. Lamp with metal chimney, easily made by rolling up some ferrotype plate and making a slit-like opening in one side. This opening should be covered by an oblong cover-glass. A glass slide, being of considerable thickness, breaks too easily. The lamp should have a wick about 30 mm. wide, so that the thickness of the flame, if taken edgewise, will give an intense light. A wide fame also enables one to get a larger image of the flame, and thus illuminate a larger object than as though a small flame were used. 2. Bull's-eye condenser on a separate stand. The engraving glass shown in Fig. /So, or the tripod magnifier (Fig. isf) answers fairly. The Steinhcil lenses are still better. S- Screen showing image of the flame inverted. The lamp and bull's-eye stand are on blocks -with screw-eyes as leveling screws. The exposure is also made in the same way, although one must have regard to the greater magnification produced by the projection ocular and increase the time accordingly ; thus when the X 4 ocular is used, the time should be at least doubled over that necessary when no ocular is employed. Zeiss recommends that when the bellows have sufficient length the lower projection oculars be used, but with a short bellows the higher ones. It is also sometimes desirable to limit the size of the field by putting a smaller diaphragm over the eye lens. This would aid in making the field uniformly Please note that these images are extracted from scanned page images that may have been digital
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