Excerpt from The Economy of the Eyes: Precepts for the Improvement and Preservation of the Sight; Plain Rules Which Will Enable All to Judge Exactly When, and What Spectacles Are Best Calculated for Their Eyes; Observations on Opera Glasses and Theatres, and an Account of the Pancratic Magnif Explanation of the Plate fronting the Title Fig. I. Is the Spectacle front recommended for Eyes in general; the distance between the centres of the openings which held the Glasses being 2 1-2 inches, i.e. the average distance between the centres of the Eyes. Fig. II. Is a portrait of the Pupil of the Eye when in a state of expansion. See Chapter XII. page 73, and No, X. of the Appendix. Fig. III. The Pupil in its most contracted state. See page 73, &c. Fig. IV. Convenient double Folding Hand Spectacles. See page 20. Fig. V. A Preserver, or the First Sight for Long Sighted Eyes, i.e. a Convex lens of 36 inches focus cut in half to shew its form, c.the thickness of it at the middle and at the margin of it. See page 27. Fig. VI. The 8th Sight, for Long Sighted Eyes or 12 Inches focus. Fig. VII. No.1 Concave, or the First Sight for Short Sighted Persons. See Chapter XIII. page 85. Fig. VIII. No.12 Concave, or the 12th Sight for Short Sighted Persons. About the Publisher Forgotten Books publishes hundreds of thousands of rare and classic books. Find more at www.forgottenbooks.com This book is a reproduction of an important historical work. Forgotten Books uses state-of-the-art technology to digitally reconstruct the work, preserving the original format whilst repairing imperfections present in the aged copy. In rare cases, an imperfection in the original, such as a blemish or missing page, may be replicated in our edition. We do, however, repair the vast majority of imperfections successfully; any imperfections that remain are intentionally left to preserve the state of such historical works.