William Crabtree

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William Crabtree (1610 – 1644) was an astronomer, mathematician, and merchant from Broughton, then a township near Manchester, which is now in Salford, Greater Manchester, England. He was one of only two people to observe the first recorded transit of Venus in 1639.

Crabtree was born in the hamlet of "Broughton Spout" which was on the east bank of the Irwell, near the area now known as "The Priory" in Broughton^[1] and was educated at "The Manchester School" which was probably a grammar school attached to the Manchester Collegiate Church, which later became Manchester Cathedral.^[2] He married into a wealthy family and worked as a merchant in Manchester. However, in his spare time, his great interest was astronomy. He carefully measured the movements of the planets and undertook precise astronomical calculations. With improved accuracy, he rewrote the existing Rudolphine Tables of Planetary Positions.

Sign commemorating Crabtree's observation of the Transit of Venus

Crabtree corresponded with Jeremiah Horrocks (who sometimes spelt his name in the Latised form as Horrox), another enthusiastic amateur astronomer, from 1636. A group of astronomers from the north of England, which included William Gascoigne, formed around them and were Britain's first followers of the astronomy of Johannes Kepler. "Nos Keplari" as the group called themselves, were distinguished as being the first people to gain a realistic notion of the solar system's size.^[3] Crabtree and Horrocks where the only astronomers to observe, plot, and record the transit of the planet Venus across the Sun, as predicted by Horrocks, on November 24, 1639 (Julian calendar, or December 4 in the Gregorian calendar). They also predicted the next occurrence on 8 June 2004. The two correspondents both recorded the event in their own homes and it is not known whether they ever met in person, but Crabtree's calculations were crucial in allowing Horrocks to estimate the size of Venus and the distance from the Earth to the Sun. Unfortunately Horrocks died early in 1641 the day before he was due to meet Crabtree. Crabtree made his will on 19 July 1644, and was buried within the precincts of the Manchester Collegiate Church on 1st August 1644, close to where he had received his education.^[4]

The recording of the transit is now seen by many as the birth of modern astronomy in Britain, ^[5]^[6] and indeed, John Flamsteed later said that that the work of Horrocks and his north country colleagues laid much of the foundation upon which his work as Astronomer Royal would stand.^[7]

On the 9th June 2004, the day after the next transit occurred as predicted by Horrocks, a commemorative street nameplate in memory of William Crabtree was unveiled at the junction of Lower Broughton Road and Priory Grove which marks the northern boundary of Crabtree Croft.^[8] A commemorative plaque was unveiled a few yards away in December 2005, at Ivy Cottage 388-90 Lower Broughton Road, which is thought most likely to have been the home of Crabtree and his family at the time when he was collaborating with Horrocks^[9]

Crabtree is also celebrated in Manchester Town Hall, where a romanticised depiction of his recording of the transit can be seen in a mural entitled Crabtree Rapt in Contemplation painted by the artist Ford Madox Brown in 1903.

[edit] Book

Chapman, Allan, '"William Crabtree 1610–1644: Manchester's First Mathematician"', Allan Chapman. Manchester Statistical Society, 1996. ISBN 0-85336-132-0..