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

  • Maddox, Ernest E. (Ernest Edmund), 1860-1933.
Date:
1893
Catalogue details

Licence: Public Domain Mark

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

Provider: This material has been provided by UCL Library Services. The original may be consulted at UCL (University College London)

    178/200
    APPENDIX. 1. —Resultant FiHsms. For those who dislike calculations, the following method of combining a vertical with a horizontal prism may be of service. Draw a horizontal line as many inches long as there are degrees in the deviating angle of the horizontal prism. From one end of this line draw another vertical line as many inches long as there are degrees in the deviating angle of the vertical prism. Then the number of inches between the free ends of these two lines equals (approximately) the number of degrees in the required resultant prism; and the inclination of the base-apex line of the resultant prism to the horizontal is given by the angle between the horizontal line and the hypothe- nuse, or resultant line, which unites the free ends already spoken of 2. —Sines^ Arcs^ and Tangents. Figure 67, to shew the relation between the arc, sine, and tan- gent, is introduced for the sake of any reader who may not be acquainted with trigonometrical ratios. Let any angle be included between the two radii of a circle, then the portion of the circumference included between the radii, as in the figure, is