. The microscope : an introduction to microscopic methods and to histology. Microscopes. 138 MAGNIFICATION AND MICROMETRY \_CH. IV For example suppose the long axis of a Necturus' red blood corpuscle measures 9 mm. on the eikonometer scale. If the magni- fication of the microscope is 200 as found above then the actual length of the corpuscle is 9 mm. â +-200= mm., or 45/*. (See A. E. Wright, Jour. Roy. Micr. Soc, 1904, pp. 261, 279; Princi- ples of Microscopy, pp. 145, 163.) A ^m t>i D. E MICROSCOPE EIKONOMETER Fig. 122. Wright's Eikonometer for Magnification and Micrometry.â [From Bec
. The microscope : an introduction to microscopic methods and to histology. Microscopes. 138 MAGNIFICATION AND MICROMETRY \_CH. IV For example suppose the long axis of a Necturus' red blood corpuscle measures 9 mm. on the eikonometer scale. If the magni- fication of the microscope is 200 as found above then the actual length of the corpuscle is 9 mm. â +-200= mm., or 45/*. (See A. E. Wright, Jour. Roy. Micr. Soc, 1904, pp. 261, 279; Princi- ples of Microscopy, pp. 145, 163.) A ^m t>i D. E MICROSCOPE EIKONOMETER Fig. 122. Wright's Eikonometer for Magnification and Micrometry.â [From Beck's Catalog.) A. Objective; B. Ocular; D. The object; E. Virtual image of the microscope; C. The Eikonometer placed over the ocular. The lens G, produces a real image on the eikonometer scale at F. This scale and real image are then viewed through the Ramsden ocular of 25 mm. equivalent focus, H. \ 197. Remarks on Micrometry.âIn using adjustable objectives (\ 27, 114), the magnification of the objective varies with the position of the adjust- ing collar, being greater when the adjustment is closed as for thick cover- glasses than when open, as for thin ones. This variation in the magnification of the objective produces a corresponding change in the magnification of the entire microscope, and the ocular micrometer valuationâtherefore it is neces- sary to determine the magnification and ocular micrometer valuation for each position of the adjusting collar. While the principles of micrometry are simple, it is very difficult to get the exact size of microscopic objects. This is due to the lack of perfection and uniformity of micrometers, and the difficulty of determining the exact limits of the object to be measured. Hence, all microscopic measurements are only approximately correct, the error lessening with the increasing perfec- tion of the apparatus and the skill of the observer. A difficulty when one is using high powers is the width of the lines of the micrometer. If the m
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