ITS

OPTICAL DEFECTS,

AND THE

ADAPTATION OF SPECTACLES.

EMBRACING

First. Physical Optics. Second. Physiological Optics.
Third. Errors of Refraction and Defects
of Accommodation, or Optical
Defects of the Eye.

WITH

SEVENTY-FOUR ILLUSTRATIONS ON WOOD,

AND

SELECTIONS FROM THE TEST-TYPES

OF JAEGER AND SNELLEN.

9925

1575

ΤΟ

DR. E. WILLIAMS,

OF CINCINNATI,

AND

DR. GEORGE STRAWBRIDGE,

OF PHILADELPHIA,

As an expression of high appreciation of their eminent ability and learning in this Department of Science, and in grateful acknowledgment of many favors,

THIS WORK

IS

Respectfully Huscribed

BY THE AUTHOR.

xi