History of Jeremiah Horrocks
printable versions: pdf
Extracted from course notes for Great Astronomers in HistoryDistance Learning
course, Centre for Astrophysics
by Paul Marston
©University of Central Lancashire
possessed one of the most original minds of the seventeenth century. A
follower of Tycho, Horrox combined a gift for instrumentation with a
theoretical genius that later won the acclaim of Hevelius and Flamsteed. His
contributions to the lunar theory were the first significant advances on the
subject since antiquity, and earned the praise of Newton himself in the
pages of Principia.”
The first observed Transit of the Planet Venus predicted & observed by Jeremiah Horrocks, 24th November 1639
Artist: J. W. Lavender 1903
Image provided by Astley Hall Museum & Art Gallery, Chorley
Gloriana, Elizabeth I, died in 1603, and James VI of
Scotland became James I of England. This first Stuart monarch incompatibly
combined autocratic royalist views with a Protestantism that was
instinctively Presbyterian. The peculiarly English brand of Protestantism
had begun with Henry VIII, and settled under his daughter Elizabeth. As
James travelled to England in 1603, he received a petition from about 1000
ministers, asking for a conference to decide on church reforms. They
objected to the sign of the cross in baptism, wanted less liturgical music,
no bowing at the name of Jesus, no profanation of the Lord’s Day, reform of
church courts and various other things. In January 1604 James himself
chaired the resulting Hampton Court Conference. Most of the “Puritan”
demands were rejected, though James did agree to some liturgical changes,
and also agreed to authorise a bible translation from which came the “King
James” version of the Bible in 1611.
James died in 1625, and his son Charles I was
crowned. The House of Commons was now dominated by “Puritans” who advocated
extempore prayer and preaching in Anglican churches, whilst the king
favoured the “High Church” party, which stressed the value of ritual and
prayer book. Charles promoted William Laud to be Archbishop of Canterbury,
and he encouraged reintroduction into churches of stained glass windows,
crosses, railed altars, bowing at the name of Jesus, and making the sign of
the cross in baptism – all things Puritans hated! The king was also in
conflict with Parliament over the conduct of various continental wars. From
Autumn 1641 the tensions between King and Parliament were rising, and the
civil war started in September 1642. Royalist forces dominated in the North
and the South West, but also in Oxford. The rise of the New Model Army in
1645 led to Royalist defeat in 1647, and eventually the execution of the
still-intriguing king in 1649. The Commonwealth then ruled until the
Restoration with Charles II in 1660.
In the England of the early seventeenth century there was little of the strong traditions of
astronomy in continental centres like Cracow, Venice, Padua or Bologna.
Francis Bacon (1561-1626) was writing to encourage the development of
science and scientific communities – but this was a vision not a reality.
Bacon’s almost exact contemporary Thomas Harriot (1560-1621) was one of few
who sprang to his mind in seeking to further his projects.
Harriot was interested in a whole range of scientific issues, including
making of lenses that he was using to make telescopes at the same time as
Galileo. He was viewing the moon through one on 26th July 1609, three weeks
before Galileo showed his to the Venetian Senate, and he was one of the
first to observe and study sun spots. He did this in great detail though
apparently left no theory about them. Harriot received patronage from
various nobles (including Raleigh), but held no academic post. William
Gilbert had published his influential work on magnetism in 1600, and (like
Harriot, Digges, and the ther small number in this set) favoured
Copernicanism. None of these, however, were involved in Keplerian type
mathematical astronomy. The universities generally neglected science and
astronomy not so much from hostility (there is no evidence of any religious
threat to Copernicanism for example) but indifference. It was not part of
the curriculum, and if students were interested in it this was as a hobby or
pastime. This changed a little in 1619 when a Chair of astronomy was founded
at Oxford (more traditionally a science centre than Cambridge), but there
was still none at Cambridge.
In religion Cambridge was, of course, exclusively
Anglican, and Oxford and Cambridge were the training centres for future
ministers in the Church of England which itself (as noted above) was
generally Puritan in sympathy – this continuing throughout the civil war and
even after the Restoration.
Details of Horrocks’s brief life are scant and
sometimes uncertain. He died on January 3rd 1641, and Dr John Wallis, who
entered Emmanuel College with Horrocks and edited his Opera Posthuma
in 1673, says that he was in his twenty third year. However, Horrocks
matriculated at the University of Cambridge on 5 July 1632, and for this he
had to be fourteen according to the regulations. His birth was therefore
between January and July 1618.
His family home was at Toxteth Park, now a suburb of
Liverpool but then a country hamlet of some two dozen houses with an area
called “Otterspool” (heigh ho!). It was once believed that his father was a
farmer William Horrocks and such a man did indeed live in Toxteth
but the evidence points more to his father as James Horrocks, a watchmaker.
The main evidence for this is a remark made by Horrocks’s friend
William Crabtree (1610-1644)
in a letter to William Gasgoigne (1612-1642) that Jeremiah’s father “died
May 3, 1641, grief for his son hastening his own death.” Flamsteed (the
first Astronomer Royal) transcribed this letter in the 1670’s, and the
Bishop’s transcript records the burial of a James Horrocks of Toxteth on May
4th in St Nicholas Church, at the Liverpool pierhead. Unfortunately the
baptismal records at this church for 1618 (the probable year of Horrocks’s
birth + christening) are missing. There is also a possibility that the family had come originally from the
Deane district of Bolton, where some have suggested Jeremiah was born. A
Jonas Horrocks was baptised in Bolton in 1622 – and Jeremiah refers to a
brother Jonas of whom there is no other record.
Assertions of his birth in Toxteth were made in the 1832 Emmanuel College
register itself, in 1859 by fellow Emmanuel student John Worthington (who
later preserved his papers), and in 1773 by Emmanuel Fellow George William
Bennet in a register of students in 1773 referring to Horrocks as a “very
curious astronomer”. Toxteth therefore seems the almost certain birthplace.
The actual place of his birth and childhood is a subject of some dispute. Toxteth Park was a former deer park, and had two
lodges when it was de-parked in 1591. By the first years of the 17th century
some twenty houses and a couple of mills had been built, causing a
contemporary reference to Toxteth as a “Hamlet without a chapel”.
One of the lodges, Lower Lodge, is the most likely place of Horrocks’ birth
and upbringing though the evidence is inconclusive.
The Lodge was demolished around 1862 to make way for a railway station now
itself derelict, and the reputed brass plate commemorating Horrocks’ birth
The Chester register of marriage licenses records the
marriage on January 17th 1615 of Jeremiah’s parents James Horrocks and Mary
Aspinwall. His mum’s brother (as various contemporary documents make clear)
was Edward Aspinwall (1567-1632) a prominent watchmaker.
Edward had matriculated from Brasenose College Oxford in 1585. Though they
did not own much in the immediate area, the Aspinwalls were a family of
standing and property.
Jeremiah Horrocks is
today comparatively unknown, but there was a flurry of interest in Victorian
days, and various myths abounded. He was often viewed as both poor and
sickly eg “There can be no doubt that Jeremiah came of impecunious parents
and that the whole of his brief life was a struggle against poverty.”
Though he went up to university as a sizar or poor scholar, and obviously
did not have great wealth, it seems unlikely that he suffered great pangs of
poverty. Lower Lodge – described as “snug” by Victorians – was a substantial
dwelling for the early seventeenth century, and not a labourer’s cottage!
Richard Mather came to teach in the new school in
Toxteth in 1611, apparently living with Edward Aspinwall. Mather went up to
Brasenose, Oxford, but returned at their invitation to begin preaching at
the chapel (which had now been added to the school) in November 1618. He
quite probably also acted as schoolmaster until his marriage in 1624 – by
1625 we know a George Whaledale was schoolmaster.
Richard Mather had Congregationalist ideas (i.e. saw the church as a body of
covenanting believers rather than the expression of state religion in a
locality). He was, however, ordained into the Anglican Church, probably in
1619. At this time (as mentioned above) the “Puritans” hoped that the state
church itself would go in their direction. Mather, however, practised
extempore prayer and steadfastly refused to wear a surplice, so was
eventually suspended in 1633 for not keeping to the proper ceremonies. He
left for America in 1635 to join other “Pilgrim Fathers” (who had sailed in
1620). The Chapel itself was never officially “consecrated” (although at one
time it was recommended to be), and Congregationalists and Presbyterians
continued to share it, comparatively unmolested, under a sympathetic refusal
to suppress them by the Earl of Derby. The Ancient Chapel today has a brass
plaque from 1856 transferred from a floor tomb to the wall, commemorating
“Edward Aspinwall” – though this is a different man of this name and
Jeremiah’s uncle clearly seems to have died in October 1632.
Jeremiah, then, was born into an artisan family of
some standing, probably comfortably if not well off. The picture of him
struggling with poverty is implausible. Instrument making was in the young
lad’s family, and dexterity in making and dealing with instruments a feature
of his upbringing. Tradition has it that his uncle Ted first interested the
young Jerry in astronomy. He may have studied at Mather’s school up to the
age of 7 years, and his family and friends’ connections were all Puritan in
sympathy. An early reference to his uncle Edward Aspinwall speaks of “a
learned and religious gentleman.”
The title “gentleman” may have been honorific – he was probably technically
Brought up in a hamlet with perhaps few children, and
serious minded and studious relatives and schoolmasters, we may wonder less
at the serious-mindedness of the young Jeremiah as he set out, aged only 14,
for Cambridge university.
Horrocks (registered Horrox) entered Emmanuel College, Cambridge, as a Sizar
on May 11th 1632. A Sizar or poor student might have to wait on tables or
perform other chores, and probably survived on very low funds, but this
route could offer a way to a degree and an appointment as a minister. The
Emmanuel College was founded by Sir Walter Mildmay in 1584 on the site of a
Dominican priory – and would (after Horrocks’s death) be graced with its
present lovely Wren chapel. It was very much a Puritan college, and its
first Master Lawrence Chadderton was a distinguished Puritan biblical
scholar and preacher. In the year Horrocks entered, there graduated one John
Harvard whose family later went with the New England Settlers and eventually
formed Harvard University. For Jeremiah to enter at age 13-14 was not
noteworthy – his friend Worthington was 14 when he entered Emmanuel in the
same year. Both,
“matriculated” together (i.e.. were sworn before the Vice Chancellor into
the university which was distinct from the college) on July 5th 1632.
Study at Cambridge was, of course, very different
then from today. The curriculum was mostly arts, divinity and classical
languages (particularly Latin). A few scraps of geometry and even classical
astronomy would be included in the arts course, but nothing thorough and
certainly nothing of the latest scientific works of Tycho, Galileo or Kepler.
Kepler had, of course, published his three laws in 1609 and 1619, and the
telescopic discoveries of Jupiter’s moons, phases of Venus, and sunspots
were known. None of this was in the syllabus, but there was plenty of time
spare and undergraduates could study such things if they wished. There were
other European centres where astronomy was taught, but Horrocks had no means
to study there. He resolved to teach himself, even though it was the
difficult mathematical astronomy that interested him:
“There were many hindrances. The abstruse
nature of the study, my inexperience, and want of means dispirited me. I was
much pained not to have any one to whom I could look for guidance, or indeed
for the sympathy of companionship in my endeavours, and I was assailed by
the languor and weariness which are inseparable from any great undertaking.
What then was to be done? I could not make the pursuit an easy one; and yet
to complain of Philosophy [i.e. science] on account of its difficulties would
be foolish and unworthy. I
determined therefore that the tediousness of
study should be overcome by industry – my poverty (failing a better method)
by patience – and that, instead of a Master, I would use Astronomical books.
Armed with these weapons I would contend successfully; and having heard of
others acquiring knowledge without greater help, I would blush that anyone
should be able to do more than I…”
What background was there in astronomy when Horrocks
entered Emmanuel? Kepler had died in 1630, having predicted a transit of
Venus and Mercury in 1631, and Venus not again until 1761. The 1631 Venus
transit was visible in America but not in Europe and was not observed, but
Pierre Gassendi observed the transit of Mercury. On this, Kepler was out by
only 6 hours, and his Rudolphine Tables were generally the most accurate
available. The Belgian astronomer Philip van Lansberge , however,
(1561-1632), was a follower of Copernicus and wanted to show that the
ancient observations were accurate and could be incorporated into a
Lansberge’s Tabulae motuum coelestium perpetuae: ex omnium temporarum
observationibus consentientes (1632) was a polemic against the
“Tychonici” (Tycho, Longomontanus and Kepler), and an attempt to explain the
difficulty of the precession of the equinoxes à la Copernicus. Lansberge’s
friend and co-worker Matinus Hortensius wrote a similarly anti-Tychonic
account in De Mercurio in Sole Visa in 1632. Horrocks, beginning his
serious study of astronomy (still, remember, only 14-15 years old) acquired
after noting the praise of them in a treatise by “D H [Henry] Gellibrand, a
Professor of Astronomy, in London”
and began to compile his own tables (Ephemerides) from the Flemish
mathematician/ astronomer’s work. Horrocks did acquire other works: in the
Trinity College library in Cambridge there is his annotated copy of Philip
Lansberge’s Tabulae Motuum, in which he lists twenty-four
astronomical authors he has read – of which, incidentally, only the
medieval Sacrobosco was from his own country!
Lansberge, however, must have seemed to be the “latest and best”,
and his trenchant criticism of the “Tychonists” including Kepler led Horrox
to focus on Lansberge to the detriment of the latter. At some point (the
chronology is uncertain) he testifies that, having realised the inaccuracies
“I broke off the useless computation, and resolved for the future with my
own eyes to observe the positions of the stars in the heavens.”
In 1635 Horrocks returned to Toxteth, aged about 17.
He did not graduate, although this was not all that unusual. Sometimes the
expense of graduating was delayed until it might be used to gain a curacy or
some preferment. We do not know what he did back in Toxteth, but he must
have spent much spare time on astronomy.
Amongst Horrocks’s contemporaries at Emmanuel were
not only Worthington (later Master of Jesus College) but also the
mathematician John Wallis, and the Cambridge Platonist Ralph Cudworth (who
in his mechanical philosophy). Perhaps it was Worthington who, shortly
before Horrocks left Cambridge, mentioned him to the young Salford cloth
merchant William Crabtreee who was to be his main scientific correspondent
from 1636-40. Crabtree had not been to university, but had learned Latin at
school and had means to buy astronomical books so would not have been in a
much different case from Horrocks. Crabtree mentions Brahe, Kepler, Galileo,
Lansberge, Descartes and Gassendi – and by 1635 realised that Lansberge’s
planetary tables were inaccurate. This is parallel to Horrocks and also
William Gascoigne who independently made the same discovery.
Crabtree wrote to Horrocks, probably at Worthington’s suggestion, begging
that he will excuse the liberty that he, a stranger, was thus taking, but
hoping that his love for those astronomical pursuits in which Horrocks so
greatly excelled would be deemed a sufficient apology. So there was formed
in 1636 the circle of the Keplerri – a tiny group of those in England
interested in Keplerian astronomy, but committed to astronomy as a
mathematical and empirical science. Crabtree confirmed Horrocks’s suspicions
that Lansberge was unreliable, and his later references (eg in The
Transit of Venus) to Lansberge are very critical – in contrast to his
admiration of Kepler.
We have to get out of our minds the picture that
Horrocks was an “amateur” astronomer, for such categories applied
anachronistically can only be misleading. Cambridge had no department and no
professor, there were no official observatories in England, there was no
obvious scientific society or group, and certainly nothing like a
degree/career structure in astronomy. Lack of funds and lack of any rich
patron were obvious problems, but that Horrocks had no recognised “post” or
qualification was almost inevitable.
Near the end of 1637 he commenced a treatise:
Jeremiae Horroccii Anti-Lansbergianus, sive disputationes in astronomiam P.
Lansbergii, quibus perspicue demonstratur, hypotheses suas nec caelo nec
sibi consentire, later retitling and rewriting it as Astronomiae
Lansbergianae censura et cum Kepleriania comparatio. One does not even
need to be able to read Latin to get the gist – Lansberge NO! Kepler YES!
Various other treatises were compiled in this time. Horrocks was writing not
only on planets, but on the moon on which his work was original and
important. He published nothing, however, lacking both the means and
probably a circle of potential buyers to do so. The Keplerri were a
tiny group in England, and not personally in contact with Continental
That he was compiling tracts in Latin, the common
scholarly language of Europe, seems to indicate an intention at least to
publish. These were not purely personal notes, but were intended to enter
upon the world at some stage. What plan he may have had in mind we cannot
In this period Horrocks was working on his lunar
theory – eventually showing that the moon’s orbit was elliptical. Horrocks
also had an interest in comets, concluding that they “move in an elliptical
figure or near to it.” He commenced a series of observations on the tides,
working on this for three months. He wrote to Crabtee about this, but no
papers survive relating to his observations or theories.
St Michael's Church: Hoole
The Church today is an active Parish Church with well attended Sunday morning services and a
Rector, Rev Harry Pugh, who appreciates its Horrocks connection (it is sometimes opened
to visitors on Wednesday afternoons in summer).
The font and two 1631 pews are still in the church, but additions were made:
- 1696: The present pulpit
- 1719 West tower and gallery
- 1858 Chancel (Horrocks chapel)
- 1859 Tower clock
- 1859 Memorial tablet
- 1874 Memorial windows
- 1994 Digital computer organ
- 1997 Floodlighting
Rev Harry Pugh in St Michaels - 2001. The Horrocks Memorial Tablet is on the left wall and just beyond it the window portraying a telescope. The window portraying Horrocks is at the far end.
On 1st June 1639 Horrocks wrote to Crabtree: “Next
week I remove to Hoole, a village about 5 miles from Preston.” Much Hoole
was a small, damp country village, set between “the Moss” to the East and
North, the wetlands of the coast and down to Martin Mere on the West and
South. We have no certainty about what he did in Hoole, but the strong
tradition is that he was tutor to the children at Carr House. The latter was
built in 1613 (as noted in an inscription on the stone porch lintel) by
Thomas Stones of London Habersdasher and Andrewe Stones the Amsterdam
merchant, for their brother John who was a farmer and landowner. Thomas also
built (of similar, probably Dutch, bricks) a chapel of ease (St Michael’s)
in 1628 – a date carved on its wooden lintel. An octagonal font was given by
John Stones in 1633, and when the chapel became a parish church in 1641
Stones was given its patronage. The curate there during this time was
Robert Fogg, who was given the new living in 1641.
Was Horrocks a curate at Hoole? He is so
named on the plaque now in St Michael’s Hoole (erected in 1859 by the
nineteenth century Hoole Rector Robert Brickel), and on the (1874) plaque in
Westminster Abbey. In the Memoir attached by Rev A B Whatton to his 1859
translation of Venus in Sole Visa, he accepts that to become ordained
“young men are now required to be twenty-three years of age”. Whatton notes,
however, a mention of Reverend Mr Horrox in a treatise by John Gadbury
(which he does not date), also one by the early eighteenth century
astronomer Costard, and by Hearne in the 1720’s. He suggests that in the
1630’s the Bishop could simply exercise discretion without any special
dispensation, and ascribes the work to “Rev. Jeremiah Horrox”. Is there
other evidence? In his work Venus in Sole Visa Horrocks states:
“I watched carefully on the 24th from sunrise to nine o’clock, and from a little before
ten until noon, and at one in the afternoon, being called away in the
intervals by business of the highest importance which, for these ornamental
pursuits, I could not with propriety neglect.”
What were these duties to which Horrocks
refers? The Victorians thought they were duties of a curate. Actually, if
the duties really were those of a curate their apparent brevity would be
very surprising. More probably they were to do with being tutor at the
house, or perhaps his “business” as any serious Christian would be to attend
the church. Most crucially, none of Horrocks’s friends or
contemporaries mention any ordination or refer to him either as “Rev Mr
Horrox” or “Rev Jeremiah Horrox”. Crabtree, for example, sadly wrote the
memorandum: “Letters of Mr. Jeremiah Horrox to me of the years 1638, 1639,
1640, until his death on the morning of 3rd January…” No title of “Rev.” is
given as it surely would have been. It seems virtually certain that
Horrocks’s supposed ordination/curacy was a myth.
He was probably called upon to pray, catechise or say grace for the Stone
family, and may even have been some kind of lay reader, though we cannot be
Carr House, where
Horrocks was probably a tutor, still stands, and now has a plaque up outside
to mark the local view that Horrocks observed the transit of Venus on 24th
November 1839 (put up by Chorley Civic Society – an event in which the
University of Central Lancashire was involved in the late ’90s). Kepler had
calculated a transit in 1631, but Horrocks realised that in fact the transit
occurs twice with an eight year gap – so would occur in 1639 but then not again until 1761/69 and then 1874/82 etc. Miss
it (next one is 2004/12) and there’s a long wait! Horrocks realised it was
coming only weeks before the event – an amazing “coincidence” unless you
have a Puritan view of providence.
The house is a listed building and retains a beauty
that is not well conveyed in a black and white picture. The most probable
room for his observation (assuming it was made here) is in the window on the
first floor above the porch. This is, in fact, the only window from which
the sun would have been observable during the whole of the relevant day 24th
November. Horrocks had also written to his younger brother and to Crabtree
in Manchester advising them to observe on this day. Crabtree did so and
Horrocks says that: “Rapt in contemplation he stood for some time, scarcely
trusting his own senses, through excess of joy.” Crabtree, however, was not
able to make any actual measurements – it was cloudy in Manchester as so
often! No one else in Europe seems to have known about the event and
Details of the observation will be given under his
works below. At this point it is useful just to say that he observed on the
day before he had calculated the transit would come, and seen nothing. He
“I watched carefully on the 24th from sunrise
to nine o’clock, and from a little before ten until noon, and at one in the
afternoon, being called away in the intervals by business of the highest
importance which, for these ornamental pursuits, I could not with propriety
neglect. But during all this time I saw nothing in the sun except a small
and common spot… This evidently had nothing to do with Venus. About fifteen
minutes past three in the afternoon, when I was again at liberty to continue
my labours, the clouds, as if by divine interposition, were entirely
dispersed, and I was once more invited to the grateful task of repeating my
observations. I then beheld a most agreeable spectacle, the object of my
sanguine wishes, a spot of unusual magnitude and of a perfectly circular
shape, which had already fully centred upon the sun’s disc on the left, so
that the limbs of the Sun and Venus precisely coincided, forming an angle of
contact. Not doubting that this was really the shadow of the planet, I
immediately applied myself sedulously to observe it.”
Horrocks had about thirty-five minutes to observe the
transit before apparent sunset at 3.50 pm, making three careful measurements
at 3.15, 3.35 and 3.45. Hoole residents may not be altogether flattered by
Horrocks’s comment at this point that the observation was made in “an
obscure village… about fifteen miles to the north of Liverpool.” Liverpool
itself, of course, in those days, was not a centre of industry, but a place
(as Whatton remarks) of “comparative insignificance”.
Horrocks’s letters from Hoole cover 8th June 1639 to
12th April 1640 after which he returned (by summer 1640) to his family in
Toxteth. We do not know what his employment was, but he continued to write
to his friend Crabtree concerning astronomical matters. He died very
suddenly on 3rd January 1641, we do not know what from. Crabtree lamented
this sudden loss, on the very day before Horrocks had planned a trip to see
him. Horrocks is believed to have been buried in an unmarked grave in
(possibly actually inside the building) the old Toxteth chapel, which is
pictured above (p. 7.4). Both Crabtree and Gascoigne died shortly afterwards
in 1644 – we do not know how Crabtree died but Gascoigne died in the
Royalist cause, probably at Marston Moor.
Horrocks’s Christian Beliefs
Allan Chapman well says:
“…as an English Protestant, Jeremiah Horrocks
would have found far fewer restrictions to scientific research than a
continental Catholic would have felt after 1633. Quite simply, the Church of
England had no policies on science whatsoever, and during the 1630s, the
English bishops were more concerned with the theology of the Divine Right of
Kings than they were with the shape of the orbit of the Moon.
What shines through Jeremiah's writings is a
sense of awe and praise for the Deity who could make a universe that was so
intricate and so beautiful. One also perceives his sense of privilege at
being the first human creature to learn of certain things - such as the
shape of the Moon's orbit - or to see the transit of Venus.”
However Chapman also says:
“We can suggest, however, that if Jeremiah was
in any way employed by the Stones family during his stay in Much Hoole, he
was not a Puritan. For the Stones family had presented a font to the parish
church of St. Michael, along with a communion chalice and platten. These
were sacramental vessels, and as such, strongly disapproved of by many
Puritans, who regarded the sacraments as 'Popish'. The Stones family also
endowed Much Hoole as a new parish in the Anglican Communion in 1641, with
Robert Fogg as the first rector. It is unlikely that a family that displayed
such marks of loyalty to the sacramental offices of the Anglican Church
would have employed a theological radical.”
This seems a very dubious argument. Puritans were
Calvinist/Reformed in theology, and not part of the Radical Reformation or
Anabaptist movement. They objected to Laud’s reintroduction of crosses,
crucifixes and surplices, and they wanted to use extempore rather than
liturgical prayers. But they made no suggestion that a Church should not
have a font or vessels to administer sacraments – how else could these be
given? The suggestion that Puritans regarded sacraments as “Popish”
is surely mistaken. That Horrocks’s family associated with the Puritan
Richard Mather and Horrocks went to the Puritan college Emmanuel would not
necessarily indicate his own views. But Horrocks makes the following comment
on Kepler – whom he calls “the most learned astronomer who ever lived”:
“Kepler’s astronomy differs from mine as his
religion: he gives the planets a divers nature (good and bad) that they may
either come to the Sun, or fly away at their pleasure, or at least (as his
second thoughts are) so dispose themselves (in spite of the Sun's magnetical
power) that the Sun is bound to attract or repel them according to that
position, which themselves defend against all the Sun's labouring to incline
their fibres. I, on the contrary, make the planet naturally to be averse
from the Sun and desirous to rest in his own place, caused by a material
dullness naturally opposite to motion and averse to the Sun without either
power or the will to move to the Sun of itself. But then, the Sun by its own
rays attracts and by its circumferential revolution carries about the
unwilling planet, conquering that natural self-rest that is in it; yet not
so far, but that the planet doth much abate and weaken this force of the
Sun, as is largely disputed afore… So just do the papists, whose free will
to do good or bad, can by its own strength go to God or fly from Him, or at
least frame their own actions, as that God is bound to save them or damn
them, volens, nolens. But I will confess myself not equally composed
of good and bad, that myself may give either to flesh or spirit the upper
hand; but rather wholly desirous to rest in myself, and wholly averse from
God, and therefore justly deserve (as the fixed stars from the Sun) to be
blown away from God in infinitum; but that God, by his Son's taking on Him
man's nature and the undeserved inspiration of His spirit, doth quicken this
dullness, nay, deadness, of my nature, yet still, ah me! how doth it choke
and weaken their operation.”
Kepler, indeed, thought that the orbits were affected
by the planets’ own magnetic forces – Horrocks’s slightly different theory
places all the determinative action in the sun itself. But on the theology
we remember that Kepler – otherwise a fairly orthodox Phillipist Lutheran –
rejected the Reformed view of predestination and advocated freewill. Horrocks
clearly here rejects the ideas of freewill taken by Kepler but also
eg by Erasmus and most of the Radical Reformation. He is advocating classic
Reformed Puritanism – every part of the conversion/salvation process in
individuals is divinely controlled and ordained. Horrocks was, in short, a
Puritan – this much was not part of any later Victorian myth. How extreme
he may have been in this view is not apparent from his comments. The Stones,
family, however, can hardly have been surprised that a man who came from
Emmanuel college held such views – and there is no reason to suppose that
they would have objected to them. The font presented by John Stones is a
perfectly plain and serviceable one, with neither ornate decoration nor even
a cross on it.||
Having, however, made some criticism of Chapman (to
whose work this present account is so much indebted) it seems appropriate to
quote appreciatively his further comment in the same work on the more
general science-religion issues of Horrocks’s times:
“Horrocks’s attitude towards science - as the
great revealer of God's design to the human intellect - was shared by the
following generations of English scientists who came to form the Royal
Society in 1660, and published his surviving letters and treatises in 1672.
John Wallis, who edited Horrocks's Opera Posthuma, was a clerical
mathematician who refused a Deanery to remain a professor. The Royal
Society's effective founder, the Oxford astronomer John Wilkins, became
Bishop of Chester in 1668, and would have come thereby to have spiritual
supervision over Much Hoole which was then in the diocese of Chester. Seth
Ward moved from an astronomical professorship at Oxford to the Bishopric of
Sarum at Salisbury, while the man who wrote the first history of the Royal
Society and its work in 1667, Thomas Sprat, became Bishop of Rochester. The
‘father of English Chemistry’, the Hon. Robert Boyle, was invited by King
Charles II to take Holy Orders so that he could receive preferment in the
Restoration Church, but refused, arguing that he felt more able to promote
the Christian faith if he were not obliged to do so by law. These men
represented the intellectual cream of Horrocks’s generation, and show how
powerfully they unified the investigations of science not only with their
Christian faith, but also with the holding of ecclesiastical office. Had
Jeremiah lived into his fifties rather than dying at 22, he could well have
been one of their number.”
Horrocks’s Work and Reputation
After the death of the
three friends, some of the relevant Horrocks papers disappeared with his
brother Jonas. Some passed into the hands of Lancashire historian
Christopher Townley where they were consulted appreciatively by Jeremy
Shakerley, who wrote three books on astronomy in the mid seventeenth
Some of the Horrocks papers passed into the care of John Worthington who had
been at Emmanuel with Horrocks.
Huygens saw a copy of “Venus in Sole Visa” and
the work was published (still, of course, in Latin) in 1661 by his friend
the self-financed Dantzig astronomer Johannes Hevelius (1611-1697). He added
his own explanations to the work (though in fact Flamsteed thought that
these were of dubious value), and appended it to his own parallel work on
In the year 1666 the Royal Society became interested
in the Horrocks papers, commissioning Dr John Wallis (who entered Emmanuel
with Horrocks) to collect and edit what he could. After many difficulties
(some papers lost in the great fire and the Royal Society generally cash
strapped!) he published in 1672 Jeremaie Horrocci Liverpoliensis Angli ex
Palinate Lancastiae Opera Posthuma – letters and papers of Horrox in
Chapman also suggests:
“Sir John Moor, the motivating force behind
the founding of the Royal Observatory, may have known Horrocks as a young
man in Lancashire, and was certainly a friend of Christopher Townley, who
preserved the Horrocks papers after Crabtree’s death in 1644… Flamsteed,
whose appointment as Astronomer Royal in 1675 owed much to Moor, had seen
and transcribed some of Horrocks’s correspondence at Towneley Hall in the
Horrocks’s work may well have highlighted the paucity of observation
facilities in England compared with those eg in Italy or Germany.
Astronomer Royal at the new Royal Observatory, was receiving insufficient
funds from the government (so what else hasn’t changed!), and having to
supplement his funds with a church living. Perhaps this helped him
sympathise with Horrocks with his financial limitations! Certainly he valued
highly Horrocks’s work. Newton’s first edition of the Principia (1687) said:
“I am not quite certain about the diameter of
the earth as seen from the sun. I have assumed it to be 40”, because the
observations of Kepler, Riccioli and Vandelini do not allow of its being
much greater. The observations of Horrox and Flamsteed make it somewhat
Newton continued to write of the ideas of
Flamsteed-Horrox. In fact, Flamsteed took what Westfall describes as a
“fatherly pride” in Horrocks lunar theory, writing (perhaps not with great
tact) to Newton on 3rd Nov 1694:
“when you have determined what corrections or
additions are to be made to that theory which it was my Good fortune to meet
with & usher into ye light, I doubt not but you will import them
to me as freely as I did the observations Whereby you limit or confirme them
The second (1713) edition of the Principia left all this out. Newton,
however, continued to value Horrocks, noting in this edition that Horrocks
was the first to show the moon as moving in an ellipse with the Earth at one
focus. In his separate work The System of the World he says
Horrocks’s lunar system as “the hypothesis of Horrox which is the most
ingenious, and, if I do not deceive myself, the most accurate of all.”
Horrocks was a natural link between Kepler and Newton, but we should not
overestimate his influence. Exaggerated 19th century claims (eg in
Whatton’s and Brinkley’s Memoirs in 1859) that Newton derived his
idea of gravity and/or inertia from him are mistaken. Horrocks speaks still
of “impetus”, and Kepler’s ideas on gravity are probably closer to
From the point of view of the history of science it is interesting to follow the
waxing and waning of interest in Horrocks – especially in his home country.
In the nineteenth century there was a surge of interest in and memorials to
Horrocks in England.
St Michael’s Church Toxteth -Park
A new Parish Church of St Michael (with iron pillars)
was built in Toxteth near to the ancient chapel (now Unitarian), and in 1826
a white marble scroll on a black slab commemorating “Jeremiah Horrox” as
“one of the greatest astronomers this Kingdom has produced” was mounted
prominently at the front of the church.
In 1859 Whatton’s translation of “Venus in Transit”
was published- this was the first English version. With it was published
Whatton’s Memoir, showing Horrocks as poor and also as almost certainly
ordained – in spite of acknowledging that he was officially too young.
The word of our God shall stand forever 1963 religion and science in fellowship 1874
The picture is pure Victorian imagination as it shows the sun projected on a sheet, whereas Horrocks actually used a piece of paper with degrees drawn on it. We do not know what he really looked like.
Born at Liverpool, Educated at Cambridge,
Curate of Hoole,
"The Wisdom of God in Creation was his study from early youth
For his wonderful genius and scientific knowledge,
Men speak of him as-
"One of England's most gifted sons."
"the pride and boast of British Astronomy."
Amongst his discoveries are
The nearest approximation to the Sun's Parallax,
The correct Theory of the Moon,
And The Transit of Venus.
But the Love of God in Redemption was to him a yet nobler theme.
The preaching of Christ Crucified a yet higher duty;
Loving Science much he loved Religion more;
And turning from the wonders of Creation to the glories of the Cross He expressed the rule of his life in these memorable words:
"AD MAJORA AVOCATUS, QUAE OB HAEC PARERGA NEGLIGI NON DECUIT"
In memory of one so young and yet so learned,
so learned and yet so pious,
This Church in which he officiated has been
Enlarged and Beautified.
In 1874, after much lobbying, a memorial was mounted
in Westminster Abbey opposite that to Newton. It reads:
In memory of Jeremiah Horrocks, Curate of Hoole in Lancashire who died on 3rd of Jan, 1641 in or near his
Having in so short a life detected the long inequality in
the mean motion of Jupiter and Saturn discovered the orbit of
the moon to be an ellipse determined the motion of the lunar apse
suggested the physical cause of its revolutionand of Venus which
was seen by himself and his friend William Crabtree on Sunday
the 24th of November (O.S.) 1639.
This tablet facing the monument of Newton was raised after the
lapse of more than two centuries. Dec. 9, 1874.
The Eyre Painting
Presently on loan from the Walker Gallery and hanging
in the Liverpool Museum Planetarium is a famous painting by Eyre Crowe BA.
The painter said that he modelled the room on that in Carr House, which he
claimed in 1891 to have visited, though the Puritan outfit seems unlikely
and elaborate equatorial telescopic apparatus unhistorical. The painting is
now very dark, and is unclear without computer enhancement.
The Ancient Chapel Memorial - Toxteth
In 1891 a tablet was put up in the (now Unitarian) Ancient Chapel of Toxteth
(pictured p. 6.4). Horrocks is still Horrox, but has been defrocked
again. The tablet finishes:
“It is believed that before going to Cambridge he was a pupil
of Revd Richard Mather the first minister of this chapel,
and that within its precincts he was buried.”
Nineteenth century and early twentieth century
English academics tended to make much of Horrocks. This seems, however, to
have faded during the twentieth century. Michael Hoskin, sometime Head of
Department of History and Philosophy of Science in Horrocks’s Alma Mater,
leaves him out of his compendious Cambridge Illustrated History of
Astronomy (1997). Kitty Ferguson, in her popular book on Measuring
the Universe (1999) mentions Harriot and Gascoigne but leaves out the
Englishman who first measured accurately our nearest planetary neighbour,
and pushed up the key measurement of solar distance to nearly 60 million
Some Technical Background
Some comment has already been given on technical
background, but we need here to expand this (which may involve some slight
repetition). To determine the distance and amount of solar parallax. Ptolemy 
had worked as follows:
The earth’s radius was known.
The moon’s distance was found by parallax (ie observing at different
points on the earths surface against fixed stars assumed very distant) and
at apogee (ie furthest away) is 64.17 earth radii (= 209 thousand miles).
The moon’s apparent diameter is equal to the sun’s in total eclipse at
apogee distance – with figures 31′ 20″ (the modern lunar figures are 29′
22″ at apogee and 33′ 31″ at perigee giving mean 31′ 5″, the mean for the
sun is 32′)
The width of the Earth’s shadow cone as the moon passes through it is
little less than 2.6 times the moon’s width.
This produced a solar distance of 1210 earth radii
(about 3.9 million miles). Ptolemy also estimated that Venus was about one
tenth of the sun’s angular diameter. The Arab/mediaeval distances differed
little, and Copernicus (as we have seen) adopted similar dimensions. Galileo
insisted in his Dialogue that these apparent diameters and distances
were wrong, but did not say what they should be.
Kepler gradually lost faith in the traditional
Ptolemaic method for estimating the parallaxes and distances. He had,
however, no obvious alternative, and resorted to considerations of harmony.
By the introduction to his Ephemerides in 1617
he arrived as a solar parallax of 2’ and a distance of about 1800 e.r. ie
7.1 million miles. By 1618 Kepler had fairly accurate relative distances of
orbits for the planets – relating, of course, to his planetary laws and in
particular the third law discovered that year. Actual distances, however,
were elusive. By now the only method for measuring parallax/distance he
thought useful was consideration of the time between lunar dichotomy (when
the moon appears as exactly a half) and quadrature (when it forms an angle
of 90o in relation to the sun). Kepler hoped that the telescope
would now enable these times to be measured more precisely – though he was
disappointed when he tried it. Kepler’s system is a mixture of the empirical
and ideas of the harmony (in mathematical terms) which must exist.
It is important to remember (and this was explored in the notes on Kepler),
that one cannot separate Kepler’s mathematical astronomy from his supposed
“number mysticism”. Kepler began from a belief that the world was made by a
rational God, committed to mathematical harmony, and that therefore would
finally be decipherable in terms of beautiful mathematics. His third law was
no more inherently rational or less “mystical” than his theory of orbits
based on the five perfect solids. Horrocks’s approach was virtually
identical in all respects. Details were changed, and the same approach led
to slightly different conclusions, but he too was looking for mathematical
harmony. In some ways, as was argued in the Kepler notes, mathematical
astrophysicists may be looking for analogous “beautiful” mathematically
based systems today – with or without reference to any God.
In any event, by 1618 Kepler had concluded that solar
parallax was nearer 1′ than 2′, and this gave a solar distance of 3469 earth
radii which (using a mean earth radius of 3960 miles) gives about 13.7
million miles (the modern figure is, of course 93.0 million). The
lunar distance Kepler found to be 59 earth radii giving 1.98 thousand miles
(the modern figure for the mean lunar distance is 2.40 thousand miles).
Kepler held that the volumes of the planets were proportional to their mean
distances from the sun, their densities proportional to the inverse root of
their mean distances, and the solar “push” (anima motrix) to make
them orbit was therefore equal. If planetary densities were equal then this
would lead to their orbital periods being proportional to their distances.
Kepler’s third law gave a different result, and so he deduced that this was
because of their varying densities.
Transits of Mercury are more common than of Venus –
about a dozen occur each century. Kepler had greatly overestimated the
apparent planetary diameters, with Venus expected as about a quarter of the
sun and Mercury similarly scaled - he therefore thought that a camera
obscura would reveal the transit. In the event only three astronomers (Remus,
Cysat and Gassendi) observed this November 1631 Mercury transit, all by
projecting with a telescope. Pierre Gassendi (or, as Horrocks calls him,
made the best observations, and was astonished at how small the planet was.
He made the apparent diameter only 20″ instead of the 15′ he had expected.
Gassendi, in fact, observing through intermittent clouds, almost
| missed it altogether until he realised that the motion of this tiny dot across the solar disc meant that it could only be Mercury. Remus made it 18″, which
fitted well his own schema that supposed that apparent diameters when seen
from the sun were the same. |
Philip van Lansberge, as noted, was Copernican rather
than Keplerian, reverted to the Hipparchic-Ptolemaic approach on measuring
distances, and was critical of Kepler’s results. His colleague and follower
Hortensius, however, defended Gassendi’s view of the smallness of Mercury
against various critics who claimed that it was some kind of optical
When Horrocks entered Emmanuel, then, in 1632, there
were exciting new theories and observations, but also many open questions.
Kepler had been dead less than two years, Galileo’s Dialogue was
about to create a stir in Italy (although about 24 years out of date since
it ignored even Kepler’s first two laws let alone the third), and the
amazing telescopic discoveries of the previous two decades had been crowned
by Gassendi’s bombshell that Mercury was tiny. We need to note that
in terms of planetary prediction (and therefore predictions of transits)
very small errors could make a big difference. It was, in fact, wrong
assumption about solar parallax and refraction that had led to Kepler (and
his assistant Jacob Bartsch) missing the fact that a second Venus transit
would occur in 1639. Astronomers were struggling to find new ways to improve
Horrocks’s Work on the Moon
Lunar theory is, of course, inherently complex, for
the moon reacts not merely to the Earth’s gravity but also to that of the
Sun, and the Earth-moon system itself reacts complexly in orbiting the Sun.
This should be borne in mind.
In his early letters to Crabtree in Autumn 1636,
Horrocks (still only 18 years old) indicated that he had found Lansberge’s
lunar theory faulty, and inaccurate in predicting the durations of lunar
eclipses (which were, of course relevant to Lansberge’s method for solar
parallax as above).
On 14th January 1637 Horrocks informed Crabtre that he now had his own lunar
theory. Only in May that year did he get a copy of Kepler’s Rudolphine
Tables. He wrote:
“I judge it to be a most perfect work…
Embracing his hypothesis as true, I have undertaken to correct his tables.”
how Horrocks tried various ways of adapting Kepler’s lunar theory. He
suggests that Horrocks was using the duration of lunar eclipses to measure
“From the apparent angular semi-diameter of
the Sun, and the horizontal parallax of the Earth, he can calculate a value
for the semi-angle of the cone of the Earth’s shadow; the calculation is
relatively insensitive to the value of the horizontal parallax, and since
Horrocks has reduced this to a lower and thus more correct value than any of
his predecessors, namely 25″, his value for the semi-angle of the cone is
almost exactly right.”
The duration of a lunar eclipse obviously depends on
both the moon’s speed and its distance from the earth (the shadow being less
when hearer), and in doing careful measurement and calculation Horrocks
found (effectively) that when the moon is in between the Earth and the Sun (ie
in syzygy) its ellipse is elongated (ie eccentricity increases). In
Horrocks’s final lunar theory, then, both the eccentricity of the lunar
orbit, and the apogee (its furthest point from the earth) oscillate. This,
in effect, was similar to an earlier model of Kepler’s, which the latter had
Wilson suggests that the reason for the divergences
between Kepler and Horrocks lay in the issue on which Horrocks was quoted
above on page 7-13. Kepler had suggested that magnetic fibres within the
planets themselves might cause alternate attraction and repulsion, which,
operating with the basic motive force of the Sun, would cause the elliptical
orbits. In his Philosphicall Exercises Horrocks explains that this
seems irrational for:
“…if the Sun be able to carry about the whole
body of ye planet, questionless it will be much more able to turn
ye friendly part to itself and so unite it to itselfe.”
Horrocks, in contrast, finds in the conical pendulum
a partial model for elliptical orbits. The pendulum bob moves in an oval and
the apsides of this oval advances just as with planetary ellipses. It is
worth quoting here from Wilson’s conclusions to his study:
“Horrocks assumes that, just as the pendulum
bob is attracted to the centre of its oval, so is the planet attracted to
the Sun; and contrary to Kepler's conception, it is never repelled. Both
pendulum bob and planet must receive a transradial impulse if they are to
move in rounded orbits instead of directly toward the centre of attraction,
and in the planet's case Horrocks locates the source of this impulse in the
rotation of the Sun. A certain imbalance between the transradial and central
forces is responsible for the forward motion of the apsides.
The only discrepancy is that the conical
pendulum produces a concentric oval, while the planetary oval is eccentric.
A wind, Horrocks suggests, could cause the oval orbit of the conical
pendulum to become eccentric; in the case of the planets, the displacement
must be due to an internal propensity. The internal propensity, Horrocks
conjectures, is a tendency for the planets to rest in the place where they
were first placed, namely, their aphelia. He devotes considerable effort to
the attempt to locate the moment of the creation of the planets, on the
fourth day of some past week, in which all the planets would be at their
If the explanation seems unbelievable to
post-Newtonians, we should yet recognize that it is an important step beyond
Kepler. It relies, not on a complicated internal structure of the planet and
Sun, but on the Sun's attraction and on properties of matter thought of as
Thus, where Kepler had explained the planetary
motions by special mechanical contrivances, designed by a providential
artificer and arranger, Horrocks now saw them as the result of the Sun's
force combined with the inertial properties of matter… He could not, of
course, account for the oscillations…
But then, even the explanation of the evection
that Newton offers in the Principia is less than satisfactory, since in
accounting for the oscillations of eccentricity and apse he uses only the
radial component of the Sun's perturbing force, and leaves the transradial
component out of account. And without Horrocks's lunar theory as a
starting-point, he would have had available neither a correct statement of
the facts of the Moon's second inequality, nor one inviting any manner of
Horrocks was hailed in some nineteenth century
eulogies as having almost invented Newtonian gravity and inertia.
This is exaggerated, and some of the things cited are actually already in
Kepler’s work. However there are aspects in which Horrocks does
form a kind of bridge between Kepler and Newton. All three men, of course,
were absolutely convinced that the cosmos was the work of a great and
mathematical designer, all three looked for a mathematical harmony in
physical nature, all three were great mathematical and empirical
Horrocks’s Solar and Planetary Work
Improved solar theory was essential for improved
planetary theory and especially planetary prediction. Horrocks therefore
worked on solar parallax, rejecting the old Ptolemaic method (still used by
Lansberge) as too full of inherent errors to be of use. Horrocks’s reasoning
was that parallax for Venus is undetectable, yet must (when Venus is near to
inferior conjunction) be four times that of the sun.
Horrocks’s figure of 14-15″ was much smaller than Kepler’s, and Horrocks
came to believe that many of Kepler’s errors were due to his inflated figure
of solar parallax.. Horrocks also calculated an eccentricity of around
0.01735 – the modern figure is 0.0167.
Horrocks’s figure for equation of centre (relating to the angle of the major
elliptical axis) was out by only +3′ – he had arrived at a more accurate
solar theory than anyone else so far.
Wilson points out that improvements in solar theory
led to improvements in planetary theory.
In a letter to Crabtree of 19th January 1638 Horrocks suggests increasing
Kepler’s figure for eccentricity of Mars of 0.09265 to 0.09292 (the present
value put on it is 0.09303). This made Horrocks’s predictions (and he made
many of his own observations to check them) accurate to within 1-2′ of arc.
For Venus, parallel improvements were of great
significance, as they led to his recognition (in Autumn 1639) that transits
of Venus occurred twice in each of the major cycles Kepler had found,
with a gap of eight years between the pairs of occurrences. Horrocks wrote
to Crabtree on 5th November 1639:
“The reason why I am writing you now is to
inform you of the extraordinary conjunction of the Sun and Venus which will
occur on November 24. At which time Venus will pass across the Sun. Which,
indeed, has never happened for many years in the past nor will happen again
in this century. I beseech you, therefore, with all my strength, to attend
to it diligently with a telescope and to make whatever observation you can,
especially about the diameter of Venus, which, indeed, is 7' according to
Kepler, 11' according to Lansberge, and scarcely more than 1' according to
The telescopic projection method was essential
because a camera obscura (as Kepler had suggested) would not work
with a Venus as small as Horrocks expected.
To observe the transit Horrocks says he: “described
on a sheet of paper a circle whose diameter was nearly equal to six inches,
the narrowness of the apartment not permitting me conveniently to use a
Onto this he projected the image of the Sun using a telescope. The kind of
telescope he used was probably Galilean rather than Keplerian in design.
During the transit he took three measurements at 3.15, 3.35 and 3.45 pm. He
found that Venus’s diameter was about 1/25th of that of the Sun. Horrocks
found the longitude and latitude of Venus from the centre of the Sun, and
demonstrated that his estimate was robust ie not altered much if there were
Horrocks calculated Venus’s apparent diameter during
the transit as 76″ and accepted Gassendi’s 20″ for Mercury. Critics had
claimed regarding Gassendi’s observation of Mercury that it appeared over
small because of the Sun’s rays shining around it. Horrocks also tried other
means to check the smallness of planetary diameters. On 7th and 29th
January 1640 he used a pinhole and moved an iron needle back and forth until
it just covered the planet to observe the exact size of Venus (and other
planets). The diameter of the needle was measured by winding a thread around
it numerous times. In arguing for a small diameter Horrocks utilised general
arguments in Galileo’s Dialogue, but apparently had not see his
Letters on Sunspots which gave estimates generally confirming Horrocks’s
From Gassendi’s and Horrocks’s measurements, Mercury
and Venus would have apparent diameters of about 28″ as seen from the sun.
Horrocks extended this mathematical harmony to other planets – though it has
to be said that the measurements made of them were by methods far less
reliable. He then asserts as a “probable conjecture”
that the Earth may also appear as 28″ from the Sun. So he challenges his
fellow Copernicans (“for I esteem not the opinions of others”):
“…what prevents your fixing of the Earth as
the same measurement, the parallax of the Sun being nearly 0′14″ at a
distance, in round numbers, of 15000 of the Earth’s diameters?”
This figure would make the Sun 59.4 million miles
away – larger than anyone had previously suggested.
Horrocks rejected Kepler’s speculations which related
planetary distances to planetary volumes. For one thing, the discoveries of
Gassendi on the size of Mercury and Horrocks himself on the size of Venus
would not fit this. Horrocks made a suggestion (which he did not know had
already been made by Remus) that is that their distances were proportional
to their diameters. He had suggested this in 1639 to Crabtree before the
transit, and now felt that it was confirmed. Horrocks was, however, well
aware that his measurements were speculative, asserting:
“I demonstrate in round numbers a very great
distance, outstripping all senses. I shall, therefore, not consider someone
to dissent from me if he adds to or subtracts from the distance of the Sun
even a thousand semi-diameters of the earth. And the same is to be said much
more of the size, with which, if you were to double it, you would not find
me disagreeing very much. For a small and imperceptible change in the Sun’s
parallax would produce all this and more…”
Horrocks was, to some extent, “lucky” in the
particular set of assumptions he made, assumptions that made him come closer
to certain figures (eg the distance of the Sun) than anyone had done
previously. The “luck”, however, went along with some careful observational
and mathematical work. Horrocks was very much in the Keplerian tradition –
he recognised the difference between speculation and reliable measurement
even though he mixed the two in an attempt to find a system that reflected
the mathematical harmony of a universe made by a loving and rational
Horrocks’s lunar theory was, as we have noted, taken
up by Newton, who never arrived at a theory he found satisfying on it. On
more general issues of the measurements made of planetary and solar
parallaxes Van Helden traces some of these in the years after Horrocks’s
death. By 1650 the old sizes were discredited, but no agreed method was
available to get better figures. Convex eye pieces had by now replaced
concave, and various micrometers were being tried Christiaan Huygens
(1629-1695) made various estimates which gave rise to a solar distance
slightly higher than the modern estimate – though some of his
assumptions were arbitrary:
Thomas Streete (1622-89), in his 1661
used Huygens’s micrometer measurements but Horrocks’s parallax figure. He
also seems to have followed Horrocks in asserting the exactitude of Kepler’s
third law. By the time of Flamsteed in the 1670’s figures fairly close to
modern ones were arrived at, though they remained uncertain. Halley tried
using the transit of Mercury in an expedition in 1676-78 to determine
parallax, but remained dissatisfied. Ironically (in view of Horrocks’s work)
he concluded that the only reliable method would be to observe the
transit of Venus – but he was unable to await the next one in 1761! Others
did, however, make careful measurements in 1761
and 1769, getting the first accurate measurements for parallaxes of Venus
and the Sun. Finally, Venus in Sole Visa established the size of our
solar system, as Horrocks had believed it would.
The primary sources for Horrocks are:
Jererniae Horrocci Liverpoliensis Angli ex Palinatu Lancastriae Opera Posthuma, edited by
John Wallis (London 1673).
A copy of this is in Liverpool Central Reference
Library, and another in the Bodleian Library – but be warned that it is all
in Latin even if the diagrams are pretty!
Memoir of the Life and
Labours of Jeremiah Horrocks, To Which Is Appended A Translation of His
Celebrated Discourse The Transit of Venus across the Sun, by Arundell
Blount Whatton B.A. LL.B. (London 1859).
This classic translation of the Discourse is
being placed on our website.
A Chapter of Romance
in Science 1639-1874: In Memoriam Horroccii. [Brickel’s work on
Horrocks, to commemorate the Building of the Brickel Vestry 1998 – available
from St Michael’s Church Hoole].
J. E. Bailey, “Jeremiah
Horrocks and William Crabtree, Observers of the Transit of Venus, 24.
November 1639”, The Palatine Note-Book II (Manchester 1882), pp.
J. E. Bailey, “The Writings of Jeremiah Horrox and
William Crabtree”, The Palatine Note-Book III (Manchester 1883), pp.
W. F. Bushell, “Jeremiah Horrocks; the Keats of
English Astronomy”, Mathematical Gazette 43, 343 (February 1959),
1-16; reprinted in the North-West Astronomers Series by the Liverpool
Astronomical Society, 1992.
Allan Chapman Three North Country Astronomers
Allan Chapman, “Jeremiah Horrocks, the Transit of
Venus, and the ‘New Astronomy’ in early seventeenth-century England”,
Quarterly Journal of the Royal Astronomical Society 31 (1990),333-571.
Allan Chapman Dividing the Circle (1990) ch 2.
Allan Chapman Jeremiah Horrocks (1994:
available from St Michael’s Hoole).
S.B. Gaythorpe, “Horrocks's Observation of the
Transit of Venus 1639, November 24, O.S.”, Journal of the British
Astronomical Association 47, 2 (December 1936), 60-8.
S. B. Gaythorpe, “Jeremiah Horrocks: Date of Birth,
Parentage and Family Associations.” Transactions of the Historical
Society of Lancashire and Cheshire,106 (1954), 23-33.
S. B. Gaythorpe “Horrocks' Observations and
contemporary Ephemerides” Journal of the British Astronomical
Association, 47 (1937) 156-7.
Lawrence Hall, The Birth-place of Jeremiah
Horrocks in Toxteth Park [In Liverpool Central Reference
Lawrence Hall, “Toxteth Park Chapel in the 17th
Century” [Rewritten for the Transactions of the Unitarian Historical
Society from a paper in July 1933, Copy in Liverpool Central Reference
H. C. Plummer “Jeremiah Horrocks and his Opera
Posthuma” Notes and Records of the Royal Society of London, 3,(1940)
W. F. Spalding, “A Country Curate” Quarterly
Journal of the Royal Astronomical Society, 12 (1971) 179-182.
R. Taton and C. Wilson (Eds) Planetary Astronomy
from the Reneaissance to the rise of Astrophysics Part A: Tycho Brahe to
Newton (1989) ch.10.
Curtis Wilson “Horrocks, Harmonies and the Exactitude
of Kepler’s Third Law” Studia Copernicana,16 (1978) 235-259.
Curtis Wilson “On the Origins of Horrocks’s Lunar
Theory”, Journal for the History of Astronomy, xviii (1987) 77-94.
Albert Van Helden Measuring the Universe
(1985) ch 10.
“Horrocks” is an East Lancashire name. He Latinised his name to Horrox
for his “official” name eg on the Emmanuel College Register and his
Allan Chapman Dividing the Circle (1990) p. 26
See John W Shirley (Ed) Thomas Harriot (1974) p. 29
Thus eg the great naturalist John Ray refused to assent to the
conditions of the Restoration and was unable to hold a post at Cambridge
– this leading to his comparative poverty.
The D.N.B. wrongly stated 1817, but see eg S. B. Gaythorpe Op Cit
on Horrocks birth etc.
Thus eg Robert Brickel A Chapter of Romance in Science 1639-1874.
A later date of death of 1652 seems improbable as a will is extant
applied in 1644.
These and a lot of other details are in W F Bushell’s “The Keats of
English Astronomy”, The Mathematical Gazette, xliii, 343 pp.
Lawrence Hall, Toxteth Park Chapel in the 17th Century p. 7.
Lawrence Hall, The Birthplace of Jeremiah Horrocks in Toxteth Park
See eg S B Gaythorpe: “Jeremiah Horrocks: Date of Birth, Parentage and
Family Associations.” Trans Hist Soc of Lancashire & Cheshire 106
W H Watts, “Jeremiah Horrocks and the Transit of Venus of 1639” (1910)
Lawrence Hall, Toxteth Park Chapel in the 17th Century gives
these and other details.
Samuel Clark The Lives of Sundry Eminent Persons in this later Age
(1683) cited by Hall.
This was in a retrospective letter to his friend Crabtree.
On all these points see Surtis Wilson in ch 10 of R Taton and C Wilson (Eds)
Planetary astronomy from the Renaissance to the rise of astrophysics,
Part A: Tycho Brahe to Newton (1989).
These wre the Uranometriam, the Tabulas Perpetuas and the
Proggymnasmate de motu Solis.
A R Whatton, Memoir (1859) p. 17.
Albategenius, Alfraganus, J. Capitolinus, Clavii Apolog. Cal. Rom.,
Clavii Comm. in Sacroboscum, Copernici Revolutioones, Cleomedes, Julius
Firmicus, Gassendi Exere. Epist in Phil. Fluddanam., Gemmae Frisii
Radius Astronomicus, Cornelii Gemmae Cosmocritice., Herodoti Historia.,
J. Kepleri Astron. Optica. – Epit. Astron. Copern. – Com. de motu Martis.
– Tabulae Rudoplhinae, Lansbergii Progymn. de motu solis., Logomontani
Astron. Danica., Magini Secunda Mobiliae.,m Mercatoris Chronologia.,
Plinii Hist. Naturalis., Ptolemaei Magnum Opus., Regiomontani Epitome, -
Torquentum. – Observata., Rhenoldi Tab. Prutenicae – Com. in Theor.
Purbachii, Theonis Comm. in Ptolom., Tyc. Brahaei Progymnasmata. –
Epistl. Astron., Waltheri Observata.
Horrocks, The Transit of Venus, p. 110.
See eg Richard Westfall Never At Rest (1980) p. 304
See Allan Chapman Three North Country Astronomers (1982) and
Dividing the Circle (1990) ch 1.
Bushell Op Cit states that Fogg was mentioned as Curate in 1632
and 1639 but does not state his source, and Chapman (in “Jeremiah
Horrocks and the New Astronomy” Qj Rl Astr Soc (1990) 333-357 note 90)
says he cannot find any such references.
At the time of writing, however, it is still repeated on some websites
eg one compiled by Professor Richard Westfall of Indiana University.
Jeremiah Horrocks On the Transit of Venus (Tr Whatton, 1859) p.
Allan Chapman Jeremiah Horrocks and Much Hoole (1994) p. 10.
This (from Philosophicall exercises Part 1 para 26) is quoted in
Brickell Op Cit, who rightly concluded that Horrocks was a
Allan Chapman “Jermiah Horrocks, the transit of Venus…” J R Ast Soc
(1990) 31 333-357.
See eg Allan Chapman Three North Country Astronomers (1982) and Jeremiah
Chapman “Jeremiah Horrocks, the transit of Venus…” note 2.
Richard Westfall, Never At Rest (1980) p. 542. Westfall has
little sympathy with Flamsteed.
O.S. = “Old Style” ie before ten days were added to adjust the calendar
See Albert Van Helden “The telescope and cosmic dimensions” in R Taton
and C Wilson (Eds) Planetary astronomy from the Renaissance to the
rise of astrophysics Part A: Tycho Brahe to Newton
See Albert Van Helden, Measuring the Universe (1985) ch. 8.
His Harmonice Mundi came out in 1619.
Actually he says: “though to illustrious Gassendi, above all others,
hail! thou who first didst depict Hermes changeful orb in hidden
congress with the sun...etc” (Venus in Transit) Poetic stuff –
modern astronomy journals cannot match it!
Curtis Wilson “On the Origins of Horrocks’s Lunar Theory” Journal of
the History of Astronomy, xviii (1987) 77-94, which also noted
Horrock’s notes in his copy of Lansberge’s tables which is in Trinity
Ibid p. 85
Ibid. pp. 86-90.
Quoted in Ibid. p. 92
Ibid. pp. 92-3.
Newton himself in Principia 2nd-3rd Edns Scholium to Prop. 35 of
Book II says “our Horrocks was the first to state that the moon revolves
in an ellipse about the Earth placed at its lower focus.” Kepler had
already done this.
See Wilson in Taton and Wilson Op Cit p. 168 etc.
These and other figures are taken from William J Kaufman’s Universe
and/or Encyclopaedia Britannica..
Wilson Op Cit p. 167.
Venus in Transit p. 121.
Venus in Transit p. 213
Van Helden (Op Cit p. 112) notes that the Belgian Priest
Gottfried Wendelin (1580-1667)had written to Gassensdi in 1635
suggesting planetary diameters proportional to distances, apparent
diameters of 28″ from the Sun, and a solar distance amounting to some
58.3 million miles – but this was unpublished!
Quoted in Van Helden Op Cit p. 112.
Curtis Wilson suggests that Newton probably first read Kepler’s third
law in this work [“Horrocks, Harmonies, and the exactitude of Kepler’s
third Law”, Studia Copernica 1978, 16, 235-259.
Bushell (Op Cit) reports that Le Gentil was sent to India to
observe the 1761 transit but war delayed his arrival. He stayed out
there eight years for the next one, but it was cloudy on the day. Coming
home he was twice shipwrecked and when he got home found he had been
proclaimed dead and his property divided up. And you thought you had
problems! Others, fortunately for science, had more success.
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