A familiar introduction to the study of polarized light; with a description of, and instructions for using the table and hydro-oxygen polariscope and microscope / [Charles Woodward].

  • Woodward, Charles
Date:
1848
Catalogue details

Licence: Public Domain Mark

Credit: A familiar introduction to the study of polarized light; with a description of, and instructions for using the table and hydro-oxygen polariscope and microscope / [Charles Woodward]. Source: Wellcome Collection.

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    over the condensers, must be turned: sideways, and fastened in a horizontal position by a bayonet catch: the staze, Fig. 17, and power, Fig. 19, are then attached, and the whole appa- ratus arranged at such an angle to the screen as to counteract the angular position of the polariscope. (78.) The most useful power for the gas polariscope or mi- croscope is that of Fig. 19, though the power, Fig. 25, may be employed for very large objects; but with reference to the crystals of calc. spar, nitre, &c. one of the modes described in sec. 73 must be adopted. (79.) When the instrument is to be used as a gas micro- scope, the condensers and polariscope must be removed, and the condensers, Fig. 24, screwed into the lantern; the stage and power are then attached and fastened with the bayonet catch as before described. (80.) If the power, Fig. 25, be substituted for that of Mig. 19, and the microscope be placed at a distance of six or seven feet from the screen, the image of a butterfly with its wings ex- tended may be so magnified as to occupy a space of fifteen feet in diameter, and yet be clearly defined. The chromatrope slides are also well exhibited with this power. (81.) Very small objects may, nevertheless, be beautifully displayed by changing the powers and condensers. The crossed lens of Fig 23, and the eye-lens of the power, Fig. 18, which is never used as such with the gas apparatus, appear to form the best condensers for the high powers; these need not, however, be separately fitted up, as there is no difficulty in changing the relative situations of any of the lenses used as condensers ; but in all cases they must be especially arranged with their most convex surfaces towards each other, and these may be immediately distinguished by observing the difference between the images of the flame of a lamp, or other object, as reflected by the respective surfaces, for the more convex the lens the smaller will be the reflected image. The bars of a window frame will be reflected in parallel lines by the plain side of a lens, but will appear to converge in proportion to the convexity of the reflecting surface, and thus a slight dif- ference of convexity may be readily detected. It is also