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Back in England
Herschel reluctantly became involved in many official duties and willingly became president of the Royal Astronomical Society. While president he wrote a preface for A catalogue of 9766 stars in the southern hemisphere, for the beginning of the year 1750, from the observations of Lacaille, made at the Cape of Good Hope in the years 1751 and 1752. The catalogue was published after the data from Lacaille’s observations were finally reduced under the superintendence of Thomas Henderson.
The University of Oxford gave John an honorary doctorate in June 1839, and he was a member of the Board of Management of the British Museum and the Board of Visitors of the Royal Observatory at Greenwich. Between 1839 and 1844 Herschel investigated photography and photochemistry using his understanding of physics and chemistry. He was the first to use the words ‘positive’ and ‘negative’ for the images. He also used glass plates, coated in silver nitrate and later silver bromide. These had a greater sensitivity to light and could be exposed in a few seconds. He realised that susceptible paper, a good lens and a chemical fixer were needed to produce pictures. His discovery that sodium thiosulphate dissolves silver salts and fixes the image was included in subsequent patents made by others. On January 30, 1839 Herschel took a picture of the 40-foot telescope at Slough using paper coated with silver carbonate solution. On July 9, 1839 he made a picture of the solar spectrum.
January 1, 1840, found the Herschel family (they had 7 children then) assembled inside the tube of the dismantled 40- foot telescope while John read a poem written by him for the occasion. Leaving some
grinding and polishing tools inside, the tube was closed, sealed and left in the grounds of
Observatory House. John’s 20-foot reflector lay in the cellar at Slough and was never used
again. It was eventually displayed at the Royal Observatory at Greenwich and in Washington DC.
HAWKHURST, 1840 – 1871
Herschel decided to move from Slough in 1840 because of the increasing urbanisation and
because he wanted a refuge where he could reduce his Cape Observations. Also Observatory
House had become too small for his family of seven children (Maria Sophia was born after
their return from South Africa). In April 1840, he purchased a house called Collingwood at
Hawkhurst, 90 km southeast of London, an “isolated country house in Kent where he spent
the remainder of his life.” (Hawkhurst. https://maps.app.goo.gl/Jci1YQXefqzsNmGK9)
Here he set up the 5-inch aperture 7-foot refracting telescope on a small observing platform on the roof.
John observed a solar eclipse on July 8, 1842. He must have travelled to see this, the path of totality passed near Lisbon and Vienna. He thought the three large prominences were enormous cloud formations. This supported his father’s model of the sun. He proposed a permanent watch over sunspot activity and Warren de la Rue began photographing the sun systematically in 1858 from England. John used “a cylindrical vessel of sheet-zinc 3.75 inches in diameter and 2.4 inches deep, filled with dark-coloured water” to measure the heat output from the sun.
While at Collingwood, John discovered that Betelgeuse in Orion was a variable star. He observed the great magnitude zero comet of March 1843 and magnitude 5.7 Biela’s Comet early in 1846. Herschel also spent many hours analysing the results of four hundred nights observing at the Cape. By 1844, with his health failing from continued trouble with rheumatism and bronchitis, he wrote, “I feel my health rapidly breaking and I have many and distinct warnings that what I have to do I must do quickly, that time is the stuff of which life is made.”
His Results of Astronomical Observations Made during the Years 1834, 5, 6, 7, 8 at the Cape
of Good Hope; Being a Completion of a Telescopic Survey of the Whole Surface of the
Visible Heavens, Commenced in 1825, was finally completed on March 7, 1847, on his 55th birthday and published in London that year. The book contained seven chapters as outlined below:
1. 1708 nebulae and star clusters, 919 objects in the LMC and 244 in the SMC
2. 2102 double stars seen with the 20’ telescope and 1081 double stars seen with the 7’ telescope
3. Brightness estimates for 2341 stars
4. Star counts done with the 20-foot telescope
5. A description of Halley’s Comet from October 1835 to May 1836
6. A summary of observations of seven satellites of Saturn and
7. Observations of sunspots.
The book earned Herschel another Copley Medal in 1847. A copy of the book was sent to
Aunt Caroline in Hanover, a year before she died aged 98.
Visitors to Collingwood included Encke in 1840, Bessel in 1842, and Airy, Babbage, Whewell, Peacock and Pritchard. He also hosted a meeting on July 10, 1847 between rivals Urbain Jean Joseph Leverrier (1811-1877) and John Couch Adams (1819-1892) after both allegedly made independent predictions for the position of Neptune. On September 23, 1846 Johann Gottfried Galle (1812-1910) at Berlin Observatory found Neptune at the position predicted by Leverrier while John Challis at Cambridge Observatory and George Airy at Greenwich Observatory failed to search for it at the position given by Adams.
Herschel was now devoting most of his time to writing and he authored a 700 page book,
Outlines of Astronomy, which was printed in at least thirteen editions between 1849 and
1902. He also wrote an article on meteorology, which was printed in the eighth edition of the
Encyclopedia Britannica and in 1845 published two papers on fluorescence.
The year 1847 saw him elected president of the Royal Astronomical Society (RAS) for the
third time but his role was largely as a figurehead because his name gave the RAS prestige.
His daughter Constance wrote The Herschel Chronicle in 1938, a collection of documents about William and Caroline Herschel. John turned 63 in 1855, the year Constance was born.
In December 1850, probably because of financial need, Herschel decided to take up public
office, and he was appointed Master of the Mint, a post that was once held by Sir Isaac
Newton. He attempted to introduce decimal currency but did not succeed. During this time he
lived in London while his family remained 90 km away at Collingwood. He no longer had
time for his scientific pursuits and, suffering from bronchitis, rheumatism and gout, he took
opium to relieve the pain. Late in 1854 he suffered a nervous breakdown and resigned from
the mint in April 1856.
Back at Collingwood he continued his solar observations and attended a meeting in Aberdeen
on terrestrial magnetism in 1859. This was “his last major public appearance.” He also
produced the General Catalogue which contained almost all the nebulae and star clusters
discovered before 1863, a total of 5079 objects. To do this he had to reduce fifty thousand
separate objects.
This was printed in the Philosophical Transactions in 1864 and enlarged in 1888 by Dreyer to become the New General Catalogue of Nebulae and Clusters (NGC), which is still used today. John found 1518 new NGC objects; 1147 galaxies, 303 open clusters, 38 nebulae, 18 planetary nebulae and 12 globular clusters between 1823 and 1838.
He also produced a catalogue of 10,300 double stars, which was published after his death and a more detailed catalogue of double stars, which was never published.
John Herschel died May 11, 1871 at Collingwood, aged 79 and was buried in Westminster
Abbey. A contemporary wrote in an obituary, “He touched nothing that he did not adorn.”
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