'Herschel's Grand Forty-feet Reflecting Telescope', 1819.
© Science Museum / Science & Society Picture Library
Engraving by J Pass of William Herschel's (1738-1822) 40-foot telescope in Slough, Berkshire, assembled in 1787 and dismantled in 1839. The massive reflecting telescope used a metal mirror four feet in diameter and weighed over a ton. A wonder of the age, it quickly became a landmark visited by the rich and famous. Illustration from 'Encyclopaedia Londinensis, or, Universal Dictionary of Arts, Sciences, and Literature' published in London, 1810-1829.