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JOHN FREDERICK WILLIAM HERSCHEL (1792-1871)

LIFE SKETCH OF JOHN HERSCHEL
Biographical information in the following section on John Herschel was mainly obtained from the 1970 book by Gunther Buttmann, The Shadow of the Telescope: A Biography of John Herschel.

WILLIAM HERSCHEL, JOHN’S FATHER
Eleven years before John’s birth, Frederick William Herschel (1738 – 1822) discovered the planet Uranus near M1 on March 13, 1781 while surveying the sky with a homemade 6-inch diameter reflector from his garden in Bath, England. William had become interested in astronomy while he was director of the Bath orchestra, and this discovery brought him great fame as an astronomer.

Five years later, in April 1786, King George III appointed William as the Royal Astronomer. John’s father and his aunt, Caroline Herschel (1750-1848), moved to Slough, where William was paid £200 per year and Caroline £50 per year to assist her brother. William made thousands of telescopes at Slough and sold them all over Europe. He also made two telescopes for himself; 20-inch aperture and 48-inch aperture reflecting telescopes. With Caroline’s help he used these to make catalogues of double stars, star clusters and nebulae.

William (aged 49) married Mary Pitt (aged 38), nee Baldwin on May 8, 1788 and John Frederick William Herschel was born in their home, Observatory House, at Slough, on March 7, 1792. As a child, John had little contact with other children. During the day, he had to maintain silence while his father slept, as William made his astronomical observations at night. Under Caroline’s guidance, John developed an interest in chemical experiments, which they carried out at her house.
(The Herschel monument at Slough. https://maps.app.goo.gl/cP3SNQ9YWRLEyype7)

JOHN’S EDUCATION
In May 1800 at the very young age of 8, John was a boarding pupil at Eton (one mile south of Slough) for a short period. “One day his mother, no doubt overanxious about his somewhat delicate health, saw her son inveigled into a boxing match by an older and stronger boy and knocked to the ground.” He was withdrawn from Eton and sent to a private school at Hitcham, where a private tutor was also provided. John was not proficient at mathematics at this stage of his life, but at age 21 became a Fellow of the Royal Society after a “brilliant mathematical investigation.”

John, aged 17, enrolled in the University of Cambridge in October 1809 and studied mathematics and physics in St John’s College. He was an exceptional student, the best candidate doing Mathematical Tripos (becoming Senior Wrangler) within the Bachelor of Arts degree. He developed close friendships with George Peacock (1791-1858) and Charles Babbage (1792-1871). They started the Analytical Society, in 1812. “The object of this society was to make known in England the modern methods of infinitesimal calculus developed chiefly in France and Germany and to replace the rather cumbersome notation of Newton’s ‘calculus of fluxions’ by the more elegant usages practised on the Continent. This ambitious project by the three undergraduates was to achieve remarkable success within five years.” Herschel and Peacock translated a book on calculus by the French mathematician Lacroix in 1816. They supplemented this in 1820, with two volumes containing examples of the French methods, and Newton’s notation was soon displaced.

During his vacations John did experiments in his own small laboratory at Slough. Chemistry at the time was undergoing major changes due to the work of Humphry Davy and Joseph Louis Gay-Lussac. He showed great enthusiasm for new ideas. In January 1814, against his father’s wishes, John decided to become a lawyer and moved to London to study at Lincoln’s Inn. William wanted John to become a clergyman, because “clerical duties would provide more leisure for the pursuit of private hobbies and scientific interest than any other profession could offer.” Much of John’s time in London was spent pursuing chemistry and mineralogy under the influence of William Hyde Wollaston and Edward Daniel Clarke. By the summer of 1815, John decided to quit law because of poor health and a lack of interest. He returned to St John’s at Cambridge as a sub-tutor and examiner in mathematics where he spent eight to twelve hours a day “examining 60 or 70 blockheads.” He took the degree of Master of Arts in July 1816, but his life was about to take a new turn.

JOHN TAKES UP ASTRONOMY
In the summer of 1816 John accompanied his father on a 275 km trip to Dawlish, a popular resort on the SW coast. William Herschel, who was then in his seventy- eighth year, had for some time suffered from various ailments brought on by advancing age and had been compelled to restrict his astronomical observations more and more.

In October 1816, soon after the holiday together, John decided to become his father’s astronomical assistant. He wrote, “I am going, under my father’s directions, to take up the series of his observations where he has left them and continuing his scrutiny of the heavens with powerful telescopes.”

John thus began the work for which he is best remembered, revising and continuing his father’s life work. William, who had made or attempted to make 2160 telescope mirrors, taught John to grind and polish mirrors. He also taught John to sweep the sky. “These (north-south) ‘sweeps’ or surveys were carried out by systematically observing all noteworthy objects – star clusters, nebulae, double stars, and so forth – in successive zones of the sky; the results were recorded in a catalogue. From personal experience the son came to appreciate the incredible physical exertions that the father’s years of night watches had entailed.”

However John never devoted himself exclusive to astronomy. His other interests included physics, chemistry, geology and mathematics as well as travel, but the study of light was his first love. He became interested in polarisation and birefringence (double refraction); he studied the interference of light and sound waves; and he investigated “spherical and chromatic aberrations of compound lenses.” In 1819 he discovered that “sodium thiosulphate has the property of dissolving silver salts rapidly and completely.” Twenty years later this contributed to the invention of photography. John also did mathematical research and contributed an article on the history of mathematics to the Edinburgh Encyclopedia. Another interest was the study of the solar spectrum. John, like his father, believed “that the Sun was a dark body surrounded by a luminous envelope.” Later in South Africa John carried out a major study of the Sun.

On January 12, 1820 John Herschel, with his friends Babbage, South, Colebrooke, Pearson and Baily established the Astronomical Society, (which became the Royal Astronomical Society in 1831). Sir Joseph Banks, then president of the Royal Society opposed the establishment of the Astronomical Society and persuaded its first president Edward Seymour to resign. William Herschel was eventually persuaded to be president and when Banks died in June 1820, the opposition ceased.

William catalogued 800 double stars and was particularly interested in binary stars. He found fifty binary stars by 1804. In 1816, soon after he decided to carry on his father’s work, John resolved to extend and improve this catalogue. He began working with James South in 1821, and together they made a catalogue of double stars using two refractors, one 5-foot and the other 7-foot in focal length with 3.75-inch and 5-inch apertures respectively. South’s refractors were made by Edward Troughton and were ideal for measuring double stars as they could measure position angles to one arc-minute. Together they searched for any movement in the double stars since William first measured them. By the end of 1823, Herschel and South had catalogued 380 double stars. South went to France with his 7-foot refractor in 1825 and catalogued a further 458 double stars. In 1828 the French astronomer Felix Savary used William Herschel’s measurements to calculate the first orbit of a binary star, Xi Ursae Majoris, “followed in 1829 by a solution from [John] Herschel (1832).”