Herschel’s Grand Forty-Feet Telescope

Herschel's Telescope

Contributor: Elsa Cazeneuve

Location: National Maritime Museum, Greenwich, London

Description: This document is a hand-coloured illustration of Herschel’s Grand Forty-Feet Reflecting Telescope, engraved by J. Pass for the 1819 edition of the Encyclopedia Londinensis (or Universal Dictionary of Arts, Sciences, and Literature), and featured in the chapter related to “Optics”. At the time, Herschel’s Forty-Feet Telescope was the largest in the world and cost over 4000 pounds, paid for by King George III. Its construction began in 1786, and was completed in 1789; the telescope was erected at Herschel’s home, near Slough. It soon became a touristic attraction and a scientific curiosity: people would travel all the way from Paris to admire this new wonder and some even likened it to the Colossus of Rhodes. Later on, the telescope was marked on the 1830 Ordinance survey map of the area. Unfortunately, Herschel’s last telescope would take years to demonstrate its worth, as it had to rotate very slowly to show various aspects of the heavens. William Herschel and his sister Caroline, who worked together, found that the telescope was difficult to set up and maintain and William’s son eventually had it dismantled in 1840. Interestingly enough, the dates of construction and demise of the forty-footer cannot but recall those of the Romantic era: Herschel’s grand telescope came to serve as a symbol of the unbounded Romantic imagination.

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The Eudiometer at Tintern

The Cavendish Eudiometer

Contributor: Tim Fulford

Location: The Wye Valley/The Royal Institution

Description: In 1800 a man inspired by Wordsworth’s visionary poetry made a trip to Tintern Abbey. Based in Bristol, he was a friend of Coleridge and Southey and was in the midst of editing Lyrical Ballads for the press; he also wrote nature verse in his own right. He was employed, however, not as a poet but as a scientific enquirer, and on his excursion to the river Wye he was armed with an improved eudiometer—the best instrument for measuring the proportion of oxygen, the gas first isolated by Joseph Priestley, in the atmosphere. ‘The Eudiometer’, he wrote, ‘that I have lately used is a very simple & commodious one – It consists of a tube about 5 inches long containing 200 grains of water – The space between the 140 & 180 grains is graduated. – This tube is emptied of water in an atmosphere when you wish to know its composition & plunged into a solution of muriate or sulphate of iron impregnated with Nitrous gas.’(1) He was Humphry Davy…

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