. The microscope; an introduction to microscopic methods and to histology. Microscopes. 40 WORKING DISTANCE WITH THE MICROSCOPE [Ch. II microscope is in focus (fig. 31, 34). Strictly speaking, it is the dis- tance between the objective front and the upper surface of a cover- glass of the exact thickness for which the objective is corrected (see table of tube-length and cover-glass thickness, Ch. IX).. Fig. 30, 31, 32. Working Distance and the Cover-glass. Slide The glass slide upon which the object is mounted. A Working distance with an uncovered object. B Working distance when a cover-glass i
. The microscope; an introduction to microscopic methods and to histology. Microscopes. 40 WORKING DISTANCE WITH THE MICROSCOPE [Ch. II microscope is in focus (fig. 31, 34). Strictly speaking, it is the dis- tance between the objective front and the upper surface of a cover- glass of the exact thickness for which the objective is corrected (see table of tube-length and cover-glass thickness, Ch. IX).. Fig. 30, 31, 32. Working Distance and the Cover-glass. Slide The glass slide upon which the object is mounted. A Working distance with an uncovered object. B Working distance when a cover-glass is used and the object is in contact with the cover-glass. The object represented by the solid black oblong ap- pears to be elevated one third the thickness of the cover to the level Obj., where it is represented by dots. The objective is elevated corresponding to the apparent elevation of the object. C Working distance when a cover-glass is used and the objects are dis- tributed in a stratum of Canada balsam. It is evident from this figure why the focus must be different for objects at different depths in the balsam. As the working distance of an objective is practically always less than its equivalent focus, one must take care to use cover-glasses thin enough so that any suitable objective can be used for studying the specimen. Furthermore, as microscopic specimens have considerable thickness, the cover-glass should be thin enough so that the objective can be lowered sufficiently to enable one to bring the lower strata of the specimen in focus without bringing the objective front in con- tact with the upper surface of the cover-glass (fig. 32).. 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 Gage, Simon Henry, 1851-1944. [Ithaca, N. Y. The Comstock publishing company
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