. The microscope; an introduction to microscopic methods and to histology. Microscopes. CH. IV] MAGNIFICATION AND MICROMETRY 117. The same corpuscle is, of course, of the same actual size, when measured in each of the three ways, so that if the methods are correct and the work carefully enough done, the same results should be ob- tained by each method. (§ 176).* Fig. 106. Ocular Screw-Micrometer with compensation ocular X 6. The upper figure shows a sectional view of the ocular and the screw for moving the micrometer at the right. At the left is shown a clamping screw to fasten the ocular to t
. The microscope; an introduction to microscopic methods and to histology. Microscopes. CH. IV] MAGNIFICATION AND MICROMETRY 117. The same corpuscle is, of course, of the same actual size, when measured in each of the three ways, so that if the methods are correct and the work carefully enough done, the same results should be ob- tained by each method. (§ 176).* Fig. 106. Ocular Screw-Micrometer with compensation ocular X 6. The upper figure shows a sectional view of the ocular and the screw for moving the micrometer at the right. At the left is shown a clamping screw to fasten the ocular to the upper part of the mi- croscope tube. Below is a face view, showing the graduation on the wheel. An ocular micrometer like this is in general like the cob-web -micrometer and may be used J'or measuring objects of varying sizes very accu- rately. With the ordinary ocular micrometer very small objects frequently fill but a part of an interval of the micrometer, but with this the movable cross lines traverse the object (or rather its real image) regardless of the minute- ness of the object. (Zeiss' Catalog). '',, 174. Obtaining the Valuation of the Screw or Filar Micrometer.—This micrometer (Fig. 106-107 ) usually consists of a Ramsden's ocular and cross lines. As seen in Fig. 107^ there are three lines. The horizontal and one vertical line are fixed. One vertical line may be moved by the screw back and forth across the field. For obtaining the valuation of this ocular micrometer an accurate stage mi- crometer must be used. Carefully focus the yjifth mm. spaces. The lines of the ocular micrometer should also be sharp. If the3" are not focus them by moving the top of the ocular up or down (\ 172 ). Make the vertical lines of the filar mi- crometer parallel with the lines of the stage micrometer. Take the precautions regarding the width of the stage micrometer lines given in | 176 (see also Fig. 10S). Note the position of the graduated wheel and of the teeth of the recordi
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