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 MAGNIFIER, FOR DOUBLE STARS, AND DAY TELESCOPES. Qui Visum, Vitam dat." BY WILLIAM KITCHINER, M.D. THE ART OF INVIGORATING AND PROLONGING LIFE; THE LOYAL, NATIONAL, AND SEA SONGS OF ENGLAND. LONDON: PRINTED FOR HURST, ROBINSON, & CO. CHEAPSIDE; AND ARCHIBALD CONSTABLE AND CO. EDINBURGH. 1824. The Illuminating and Magnifying Powers and Prices of Newtonian, Gregorian, Cassegranian, and Herschelian Reflectors, and Galilean, Huygenian, and Achromatic Telescopes, of from 3 Inches to 7 Feet Focus, being Calculated and Described in Plain Terms which all Persons may easily understand. To which will be added, An Appendix from the Writings of SIR ISAAC NEWTON, SIR WILLIAM HERSCHEL, &c. and Original Communications from Eminent Practical Opticians of the present time, on the Construction and Use of Telescopes. - LONDON: PRINTED BY J. MOYES, GREVILLE STREET. PAGE SPECTACLES WITH PLAIN GLASSES.. III. CASES OF PERSONS WHO COULD NOT 20 and 34 The time that the First Glasses of 36 Inches focus will assist the Sight |