. Animal micrology; practical exercises in microscopical methods. Microscopy -- Technique; Microscopes -- Technique. 144 Animal Micrology left outstanding form the defect known as a secondary spectmm. In the apochromatic objectives (p. 146) three rays are brought to one focus, leaving only a slight tertiary spectrum. NOMENCLATURE OR RATING OF OBJECTIVES AND OCULARS Oculars.— Different makers, unfortunately, use different sys- tems in marking their lenses to indicate relative powers of mag- nification. In the case of lettering the system is wholly arbitrary; the only rule is that the nearer to
. Animal micrology; practical exercises in microscopical methods. Microscopy -- Technique; Microscopes -- Technique. 144 Animal Micrology left outstanding form the defect known as a secondary spectmm. In the apochromatic objectives (p. 146) three rays are brought to one focus, leaving only a slight tertiary spectrum. NOMENCLATURE OR RATING OF OBJECTIVES AND OCULARS Oculars.— Different makers, unfortunately, use different sys- tems in marking their lenses to indicate relative powers of mag- nification. In the case of lettering the system is wholly arbitrary; the only rule is that the nearer to A the letter is, the lower the magnifica- tion. When the objective bears a figure it is usually indicative of the magnify- ing power of the part marked. Thus a y1^ inch objective magnifies ap- proximately 120 diamet- ers; a J inch,80 diameters; a 4 inch, 20 diameters; a a 1 inch, 10 diameters: a 2 inch, 5 diameters; and so on. This means that an objective which forms an image 10 times the real diameter of the object itself, on a screen placed 10 inches (the conven- tional distance of vision) from its back lens, is rated as a 1-inch objective. If it FIG. 58.—The Zeiss HIB Stand with Diaphragm- formed ail image only 5 Carrier (B) and its Key (C). ,. » m c. • t-fi times the real diameter ot Zciss is represented in America by The Scientific Shop, 324 Dearborn street, Chicago, 111. ^Q ohjecf; ft WOuld be a 2- inch objective, if 30 times, a j-iucli objective, and so on. Such magnification is termed the initial iii<iircr of the 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 Guyer, Michael F. (Michael Frederic), b. 1874. Chicago, The University of Chicago Press
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