The outlines of physics: an elementary text-book . !ommonly a fixed cross hair to mark;he middle of the field of view, andsometimes the moving hair is sup-planted by two crossing each other atan oblique angle. In the latter =F^ Fig. 401. Fig. 400. case the appearance of the field is that represented in Fig. is a more elaborate device than the eyepiece scale, and admits2f 434 THE OUTLINES OF PBTSICS of greater accuracy of observation. Like the former, however, it mustbe calibrated by reference to a scale or an object of known size placedunder the microscope. 3. Method of the Mi
The outlines of physics: an elementary text-book . !ommonly a fixed cross hair to mark;he middle of the field of view, andsometimes the moving hair is sup-planted by two crossing each other atan oblique angle. In the latter =F^ Fig. 401. Fig. 400. case the appearance of the field is that represented in Fig. is a more elaborate device than the eyepiece scale, and admits2f 434 THE OUTLINES OF PBTSICS of greater accuracy of observation. Like the former, however, it mustbe calibrated by reference to a scale or an object of known size placedunder the microscope. 3. Method of the Micrometer Stage. —In this method the micrometerscrew is attached to the stage of the microscope, and the object ismoved through the field of view by turning the screw. There is inthe eyepiece a fixed cross hair. This method has one advantage overthe foregoing, namely, that it is the movement of the object itselfwhich is measured. The pitch of the screw being known, there-fore, it is not necessary to calibrate the instrument. Sometimes themicrome
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Keywords: ., bookcentury1800, bookdecade1890, bookpublishe, booksubjectphysics
