instrument's name honors John D. Hooker, a businessman who donated funds to make
the mirror. The telescope was a mechanical masterpiece, and its mirror, 2.5 meters
(100 inches) in diameter, remains the largest solid plate glass mirror ever made.
The giant telescopes on Mount Wilson were made possible by the introduction of
glass mirrors. A method for depositing an extremely thin, even coating of silver
on glass was developed in the mid-19th century. Glass mirrors had many advantages
over the metal mirrors used by William Herschel and others. They held a higher
polish and could be stripped and recoated quickly when they tarnished, without
having to be repolished.