. The microscope : an introduction to microscopic methods and to histology. Microscopes. 134 MAGNIFICATION AND MICROMETRY [ CH. IV curate stage micrometer must be used. Carefully focus the -j-J-j mm. spaces. The lines of the ocular micrometer should also be sharp. If they are not focus them by moving the top of the ocular up or down (§ 188). Make the vertical lines of the filar micrometer parallel with the lines of the stage micrometer. Take the precau- tions regarding the width of the stage micrometer lines given in § 197 (see also Fig. 123). Note the position of the graduated wheel and of th
. The microscope : an introduction to microscopic methods and to histology. Microscopes. 134 MAGNIFICATION AND MICROMETRY [ CH. IV curate stage micrometer must be used. Carefully focus the -j-J-j mm. spaces. The lines of the ocular micrometer should also be sharp. If they are not focus them by moving the top of the ocular up or down (§ 188). Make the vertical lines of the filar micrometer parallel with the lines of the stage micrometer. Take the precau- tions regarding the width of the stage micrometer lines given in § 197 (see also Fig. 123). Note the position of the graduated wheel and of the teeth of the recording comb, and then rotate the wheel until the movable line traverses one space on the stage mi- crometer. Each tooth of the recording comb indicates a total revolution of the wheel, and by noting the number of teeth required and the graduations on the wheel, the revolutions and part of a revolution required to measure the y-J-j- mm. of the stage micrometer. Fig. 119. Filar Micrometer Ocular. This filar micrometer ocular is of the Ramsden type and consists of a positive ocular with a moveable hair line and two reference lines at right angles to each other as shown in A. The moveable line must be carried over the entire length of the object to be meas- ured by rotating the drum. A. Field of the filar micrometer showing the moveable and the cross lines, and the comb. The teeth serve to measure the total revolutions of the drum. (Cut loaned by the Bausch & Lomb Optical Co.) can be easily noted. Measure in like manner 4 or 5 spaces and get the average. Suppose this average is i}( revolutions or 125 grad- uations on the wheel, to measure the j-^j mm. or 10// (see § 182), then one of the graduations on the wheel would measure io/< divided by i25=.o8;U. In using this valuation for actual measurement, the tube of the microscope and the objective must be exactly as when obtaining the valuation (see § 187, 194).. Please note that these images are extracted
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