Lenses—how to determine their Focal Lengths 12 Brazil Pebbles—Periscopic and Parallel Lenses—Process of 13 Working—Tests of Quality—and Experiment 14 Railroad Spectacles—Neutral Tint Shades 16 Country-made Spectacles—Trial Box of Sight 18 CHAPTER III. A Visit to the Optician—Rules for selecting Spectacles 21 Spectacle Frames—Russian Remedy for Short Sight 24 Solid Blue Steel Spectacles 26 Anti-pressure Spectacles—Single Eye Glasses injurious 27 Prices of Spectacles 28 CHAPTER IV. Specious Quackery—Testimonial Writers 30 Amber Spectacles analysed—Puffing Advertisement 33 Opinions of Dr. Neill Arnott, Dollond, Curtis, &c. 34 Absurdity and Ignorance of Puffing Advertisers, 36 CHAPTER V. Instances of Gross Imposition—Clarified Crystals and Coloured Pebbles! 37 Naval and Military Officers—Definition of LAW 39 Ladies and Spectacles—Persevering Roguery 41 An Old Clothes Man Metamorphosed 43 CHAPTER VI. Specimens of Puffing Advertisements, 44 Royal Patronage—Cataract Alarmists 45 Abstract of Act of Parliament 46 Newspaper Paragraphs, 50 CHAPTER VII. Provincial and Metropolitan Scheming 52 Public Cautions—Tricks at Brighton 56 Liverpool Mercury—Parabolic Cheats 60 CHAPTER VIII. Correspondence with the Duke of Wellington 61 —— Frederick Tyrell, Esq. J. Hodson, Esq. 62 Signatures of J. Soden, Esq., J. F. Ledsam, Esq., —— Alexander, Esq. 64 Correspondence with Robert Keate, Esq. 64 Pretended Discoveries, Humorous Scraps, &c. 66 SPECTACLE SECRETS. CHAPTER I. “Science should be stripped of every thing that tends to clothe it in a strange and repulsive garb, and especially every thing that, to keep up an appearance of superiority in its professors over the rest of mankind, assumes an unnecessary guise of profundity and obscurity, should be sacrificed without mercy.”—SIR I. F. W. HERSCHEL.