A Popular History of Astronomy During the Nineteenth Century Fourth Edition
CHAPTER VI
INSTRUMENTAL ADVANCES
Two Principles of Telescopic Construction--Early Reflectors--Three Varieties--Herschel's Specula--High Magnifying Powers--Invention of the Achromatic Lens--Guinand's Optical Glass--The Great Rosse Reflector--Its Disclosures--Mounting of Telescopes--Astronomical Circles--Personal Equation 108