John Stevens Henslow

1796–1861

John Stevens Henslow was a brilliant academic, an outstanding country parson and a generous philanthropist. He spent much of his working life in the University of Cambridge, and made his name in the wider world as mentor to Charles Darwin. Owen Spencer-Thomas explores the remarkable life of this talented Georgian and early Victorian figure.

Although John Stevens Henslow is best remembered as friend and mentor to Charles Darwin, he also made a lasting contribution within the academic setting of Cambridge University and the education system of his day.

Henslow was born on 6th February 1796 in Rochester, Kent. He was the eldest of eleven children. His father, who was a solicitor, encouraged him to develop his enthusiasm for natural history and, at a very early age, he became an avid collector of botanical specimens.

In 1814, Henslow entered St John’s College, Cambridge, where he studied science. He graduated in 1818, and then renewed his interest in natural history, making geological expeditions to the Isle of Wight and the Isle of Man with his Cambridge colleague Adam Sedgwick. The two men established the Cambridge Philosophical Society in 1821. The following year Henslow was offered the chair of mineralogy in the university, which he took up with great enthusiasm.

Two years later he was ordained and, in 1825, became the curate at Little St Mary’s Church, Cambridge. In the same year, he was offered the position as Regius Professor of Botany – a post he held for the rest of his life.

Henslow was a popular, progressive teacher, both in the classroom and in the field. His natural enthusiasm made botany one of the more popular subjects at the university. Rather than pampering his students, he encouraged them to make their own observations, giving them plants and asking them to examine and record the characteristics of the structures they found. He took them on field trips, and invited them to his house for dinner, where they discussed a range of scientific topics more informally.

During his time at Cambridge he extended the Botanic Garden and remodelled the 40-acre site between Bateman Street and Brooklands Avenue, making it world-famous.

However, this academic clergyman is best remembered as friend and mentor to his pupil Charles Darwin, and for inspiring him with a passion for natural history. The two met in 1828. Soon after they were introduced, the young Darwin, who was supposed to be studying theology at Christ’s College, began attending Henslow's Friday-evening scientific soirées.

Henslow became his tutor, and it was not long before he marked out Darwin as a promising student. His star pupil was to become a lifelong friend – a remarkable alliance which persisted, in spite of Darwin’s eventual atheism and Henslow’s never-failing liberal Christian belief.

After Darwin’s graduation, Henslow persuaded him to study geology, and arranged for him to become a field assistant to Adam Sedgwick and help on some research in north Wales. Little did any of them realise just how soon Darwin would be putting his newly acquired skills to the test.

Henslow was offered a post as naturalist to sail aboard the survey ship HMS Beagle on a planned two-year trip to survey South America, but his wife dissuaded him from accepting. Seeing a perfect opportunity for his protégé, the good-natured clergyman wrote to the ship’s captain, Robert Fitzroy, telling him that Darwin was an “acute observer” and the ideal man to join the expedition team.

A few months later, Darwin set sail for the South Seas and what turned out to be a round-the-world voyage of nearly five years – including a visit to the Galapagos Islands, where he discovered unique flora and fauna.

During the Beagle voyage, Darwin and Henslow wrote to each other as often as the primitive postal system would allow. Henslow encouraged Darwin, and advised which specimens to collect, recommending the best way of preserving and shipping them.

As the main recipient of Darwin’s massive collection of scientific samples, Henslow passed them on to the appropriate experts to analyse. He published extracts of Darwin’s letters in scientific journals and presented summaries to the Cambridge Philosophical Society.

When, in 1836, Darwin returned home, Henslow helped him obtain funding to publish his zoology books. His scientific credentials and future scientific career were assured – thanks largely to Henslow.

The following year, Henslow was appointed Rector of the neglected parish of Hitcham in Suffolk, where he was to remain for the rest of his days. However, the great university academic was an uninspiring preacher. His congregation was barely big enough to fill a single pew. So he decided to concentrate on improving his parishioners’ well-being through scientific, rather than spiritual, enlightenment.

It was the hungry 1840s. Severe economic depression and serious crop failures across Europe brought about a major famine. Henslow reacted to the crisis by letting 52 allotments on his glebe land. Local employers were so infuriated that, at a vestry meeting, they resolved to refrain from hiring any labourers who rented an allotment. Nevertheless, the scheme caught on and, two decades later, 150 were being cultivated in the village.

Henslow engaged in many other philanthropic endeavours. He set up a village school – teaching some of the lessons himself. Among many books, he published a standard work on the flora of Suffolk. He identified the plants which the children of the school found in his parish and by 1860 had recorded 406 species. A hundred years later, 60 of these could no longer be found.

He founded the Ipswich Museum in 1847, becoming its president in 1850. He administered local charities, and organised educational excursions to various venues, including the 1851 Great Exhibition.

Henslow’s energies were mainly devoted to improving the lot of his parishioners, but his influence was felt far and wide. He showed Irish farmers, stricken by the potato famine (1845–46), how to extract starch from rotten potatoes, and gave public lectures on the fermentation of manure.

He continued to carry out archaeological excavations and made numerous discoveries. He tutored Queen Victoria’s children, and kept in touch with the wider scientific community, including his celebrated former pupil, Charles Darwin.

While on holiday in Felixstowe, he discovered phosphate-rich coprolites nodules – fossilised faeces or bones – in the Red Crag cliffs. He advocated using these, and also the large phosphate deposits in the Cambridgeshire greensand, to nurture agricultural crops. Although he derived no financial benefit, these discoveries led to the establishment of the fertiliser industry with famous names, such as Joseph Fison, setting up works in Hauxton, near Cambridge, and Ipswich. 

In 1860, the year before his death, Henslow chaired the legendary debate at the Oxford University Museum of Natural History, in which Thomas Henry Huxley and Henslow’s son-in-law, Joseph Hooker, did battle with the Bishop of Oxford, Samuel Wilberforce, over Darwin’s theory.

The following winter, Henslow became seriously ill with a heart condition. His health continued to grow worse. Realising that the end was near, with Hooker standing vigil, he bade farewell to numerous visitors called to his bedside. Conspicuous by his absence was Charles Darwin, by now a virtual invalid himself.

John Stevens Henslow died after a bronchial attack on 18th May 1861. He is buried in Hitcham churchyard. Charles Darwin wrote to Hooker, saying, “I fully believe a better man never walked this earth.”

© Owen Spencer-Thomas 

Revised 18 March 2012  

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The Revd Professor John Stevens Henslow 1796-1861

The Botanic Garden, Cambridge

Henslow’s colleague The Revd Professor Adam Sedgwick

Queen Victoria with her five children