The clinical use of prisms and the decentering of lenses / by Ernest E. Maddox.

  • Ernest Edmund Maddox
Date:
1889
Catalogue details

Licence: Public Domain Mark

Credit: The clinical use of prisms and the decentering of lenses / by Ernest E. Maddox. Source: Wellcome Collection.

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    J> PRISMS. The sections a d c and b e f being made in planes perpendicular to the refract- ing surfaces, are named ''principal sections The remaining surface d. c e f \?, the '' base'' nasr Fio. 2.—The same prism in section. When prisms are designated square, rectangular, circular, and so forth, it is of course understood that these expressions do not, as indeed they could not, apply to the angle of the wedge, but to the shape of the two refracting surfaces. Clinical prisms are almost universally circular to admit of their insertion in the same trial-frame as the lenses : the design in Fig. 3 shews how a circular prism is related to, as though it were cut out of, a rectangular one. PiS' 3'—A hypoihetical illustration to shew the relation of a circular prism to a rectangular one.