Cambridge, Peterhouse, MS 75.I
Contents
Introduction:
The Equatorie of the Planetis in Peterhouse MS 75.I describes an instrument for calculating the
positions of the planets. On the evidence of its calendar references the text was
probably composed in 1393. For an
astronomical work of this date, it is remarkable for being written in English. When
it was brought to public attention
by Derek J. Price in 1951 it naturally invited comparison with Chaucer’s A Treatise on the
Astrolabe. Accompanying the Equatorie, and in the same hand, is a set of tables, one
of which contains the note ‘Radix Chaucer’ (f. 5v and see image right, taken when the manuscript was disbound). The consequent
possibility that the Equatorie was Chaucer’s own composition is an issue that has occupied the
attention of many scholars; however, this has now been resolved. The writer has been
identified as John Westwyk, a
Benedictine monk of Tynemouth Priory and St Albans Abbey, whose life was one of dramatic
contrasts (Rand 2014). |
| The astronomical content of the manuscript is also of considerable value in its
own right. The entire text
(excluding the contents of the tables) has been transcribed. A key to the conventions
used in the transcription is
available here, and a key to the numerals used in
the manuscript can be accessed here
|
Virtual model
Video tutorial
In conjunction with the digitisation of the manuscript, a digital model of the equatorium
it describes has been
produced, following the instructions and diagrams in the manuscript. This fully-functional
interactive equatorium can
be accessed by clicking on the link above (left); we recommend opening it in a separate
window if you wish to view it
alongside the manuscript. Those visitors whose browser does not support the interactive
model, or who require guidance
on the way it works, are recommended to view the video tutorial above (right).|
Writing process
|
| The text of the Equatorie of the Planetis is clearly an author’s or translator’s
autograph. It is unusual in several respects. Most obviously because it is in English
– astronomical texts from this
period are almost exclusively written in Latin – but also because of its distinctive
appearance and the way it shows
the writer at work.
The pages are very large (see Detailed description), as is the writing, which usually
goes across most
of the width of the page, in long lines which are not straight. There is no line ruling.
The space between words and
between lines is exceptionally generous. The script used is a practiced casual one,
not a formal scribal one. However,
the man is no amateur as a writer – he was clearly used to drafting and writing with
an eye to later copying, which is
what we find him doing here. He is composing a text, and apparently at the same time
attempting to produce a fair copy
with little scope for misunderstanding. The result is a tendency towards clarity at
the expense of neatness. His most
frequent way of correcting his text is through erasure (i.e. scraping dried ink off
the parchment with a knife). This
is obvious even to the naked eye, but under ultra-violet light (UV) it becomes clear
that words have been erased and
replaced by others in virtually every line. The majority of the erasures have been
written over with no sign that the
space available was too small or too ample, so we may assume that the changes were
made when drafting. The advantage
of this is obvious. Although interlinear emendations are unavoidable at a later stage
of checking the text, there is
less scope for ambiguity and error if they are kept to a minimum from the start. Very
occasionally the writer also
deleted by means of cancellation (drawing one or more straight lines through the word
or passage he wished to delete)
[f. 71v11; most of f. 76r] and of expunction
(placing a dot under each letter to be left out) [f. 75v1]. He has also used
dissolution (sponging the ink of the word or passage in question until it dissolved),
but we cannot tell how often.
Dissolution required well spaced words and lines, and could only be done while writing,
when there was no text below
or to the right. Signs of successful dissolution are virtually impossible to detect
with the naked eye because the
surface remains smooth. However, at f. 78r4 a smudge of pigment is left, signalling
something underneath (line final ‹shal› visible under UV). Three instances around
the rift in f. 77 (ff. 77r21 ‹the›, 77v20 ‹the› and 77v23 ‹thre›) show dissolved words which are only
visible
under UV, and only because they have not been written over.|
Having composed a clear, relatively clean and above all legible draft, which could
serve as an exemplar
for further copying, the writer went on to the next stage, checking the contents and
aiming for ease of understanding.
This resulted in eighty additions and emendations to the text. These have been inserted
in the wide spaces between the
lines, half of them accompanied by a caret mark on the line to indicate where they
should go. Occasionally they alter
the substance [f. 71v11], but most frequently they add clarity to the instructions
[f. 71v6], and sometimes they produce a more English syntax. The great majority
of the insertions without a caret are Latin or anglicised Latin terms which amplify
the text or clear up ambiguous
points. The remaining twelve are glosses, i.e. English words or concepts in the body
of the text are glossed by
interlinear Latin synonyms (‹punctus› above ‹poynt› on 73v1, ‹id est punctus› above
‹prikke› on f. 73r31). How (if at all) the writer intended the glosses to go into
the text, is not obvious. In England in the 1390s it was the Latin astronomical terms
which provided the points of
reference and were familiar to his readers. No English vocabulary had as yet been
firmly established and it is common
in English medical and scientific treatises from this period to introduce English
technical terms in a text by pairing
them with Latin synonyms (as does the Equatorie writer himself on f.
78v14).|
The text of the Equatorie would appear to be partly original composition based on
the writer’s own practical experience (but perhaps not with an equatorium of the size
he describes) and partly
translation from a Latin source (or sources). Until a source has been identified,
however, the proportion of
translation to composition must remain the object of speculation.|
John Westwyk
|
| Because of the autograph nature of the text, some scholars have seen the Equatorie not
only as a possible addition to the Chaucer canon, but perhaps also a text in Chaucer’s
own hand. No example of
Chaucer’s handwriting was known in the early 1950s when Price’s edition appeared,
and none has come to light since.
Subsequent research (Rand Schmidt 1993) showed that the Equatorie hand differs on important
points from those of all the proposed Chaucer autographs in the Public Record Office
(which in turn differ from each
other). Although the Equatorie is largely in the type of London dialect which Chaucer could
have been expected to use, it could not be shown to be distinct to him. Quantitative
studies of the prose style showed
that the Equatorie is not sufficiently like the prose texts known to be Chaucer’s, and at the
same time sufficiently unlike comparable non-Chaucerian texts, for the Equatorie to be
identified as Chaucer’s on those grounds. The case for Chaucer’s authorship of the
Equatorie of the
Planetis rested on insufficient evidence.
However, new evidence has now come to light (Rand 2014, http://dx.doi.org/10.1080/00393274.2014.982355).
Oxford, Bodleian Library MS Laud misc. 657 is written in the same hand as the Equatorie. The
writer was a Benedictine monk who signs himself Johannes de Westwyk, and is referred
to as John Westwyk in
contemporary records. A detailed comparison of the script in the two manuscripts is
included in Appendix 1 of Rand
(2014). The Laud manuscript contains two texts by Richard of Wallingford, Abbot of
St Albans (1292-1336): his Albion, and the Rectangulus. The latter is a straightforward copy,
whereas the text of the former has been adapted to John Westwyk’s circumstances. John
appears to have been admitted to
the order at St Albans, having come from a local family, and to have had his first
training in astronomy there. At
some point in or near 1381, he was made to go, or chose to go, to St Albans’s daughter
house at Tynemouth on the
Northumberland coast. Tynemouth Priory was then in a state of disrepair and subject
to constant attacks from the Scots
over the border. It was frequently used as a ‘penal colony’ for recalcitrant St Albans
monks, but John may have been
sent there to teach. He is perhaps most likely to have written Laud misc. 657 before
he went north. At St Albans he
would have had easy access to exemplars for the two Wallingford texts, and to the
requisite amount of parchment of
uniform quality. He amended the instructions in the Albion text to accord with the latitude of
Tynemouth, and with the more restricted needs of those leading a cloistered life.
By 1382/83 John Westwyk was however ready to get away from Tynemouth. In the late
autumn of 1382 Henry
Despenser, Bishop of Norwich, had launched a plan for a campaign against the anti-pope
in Avignon in the shape of a
crusade against Flanders. The Pope had given the Bishop the right to raise troops
and funds in exchange for
indulgences, which he successfully did. Members of the clergy had permission to take
part in this holy war as
soldiers. The expedition also had royal approval and Parliament’s support. When it
left for Calais in May 1383, seven
monks from St Albans and its daughter houses had joined, and John Westwyk was one
of them.
At first the campaign was successful and significant battles and towns were won,
but the Bishop’s army
soon suffered losses and the troops caught dysentry. By late September there had been
a complete reversal of fortune
and the troops trickled back to England. The chronicler Thomas Walsingham reports
that the six monks from St Albans
who survived were welcomed back by the abbot, but never regained their former health
(British Library, MS Cotton
Claudius E.iv, vol. 2, f. 239vb; printed Riley, ii, 416).
There is nothing to indicate that John Westwyk returned to Tynemouth, but nothing
is known about him for
the next ten years. However, in 1393 he was writing the Equatorie of the Planetis in a location
where he had easy access to large sheets of parchment. He wrote it in English, in
a dialect close to a London one, but
with a number of non-London dialect forms. Some of the accompanying tables in his
hand contain Oxford references, a
greater number contain London ones.
The next mention of John Westwyk is in May 1397, when he is recorded in the Lateran
Regesta as a monk of
St Albans and as having procured an indult for the confessor of his choice to grant
him, being penitent, plenary
remission of sins as often as he pleases (Archivum Secretum Vaticanum, Lat. Reg. 45,
f. 175v; calendared in Bliss
& Twemlow, v, 42). This appears to be the last extant reference to him. It seems likely
that the indult was an
end-of-life one, and that he died soon after.
| Kari Anne Rand| November 2014|
|
Equatorium design and astronomical tables
|
| Although similar instruments are described in other treatises dating from the thirteenth
and fourteenth
centuries, this precise design of planetary equatorium is unique to the Peterhouse
manuscript. Ff. 71v-74r explain first how to make the instrument; ff.
75r-78v explain how to use it to find the longitudes of the Sun, Moon and planets, and the
latitude of the
Moon. Celestial latitude and longitude are coordinates in the sky: longitude is measured
around the ecliptic (the path
of the Sun’s annual motion through the fixed stars, in a plane angled at around 23°
to the celestial equator), in
degrees from 0 to 360° starting from the vernal equinox (where the ecliptic and celestial
equator intersect); latitude
is measured in degrees from 0 to 90° north or south of the ecliptic.|
The design is a simplification of the Ptolemaic model of planetary motion. In this
model each planet
moves at a constant velocity around an epicycle; the centre of that epicycle itself
moves around a deferent circle, at
a velocity which is constant with respect to another point, the equant centre. For
the planets Venus, Mars, Jupiter
and Saturn, the equant centre (E) and deferent centre (D) are fixed on a line running
from the Earth (W) to the
planet’s apogee (A, called “aux” in the treatise); D is midway between W and E. Thus
five pieces of information are
necessary to calculate a planet’s longitude: the direction of A, measured as an arc
from the vernal equinox (♈); the
size of the planet’s eccentricity (i.e. the displacement of D and E from W); the relative
sizes of its deferent circle
and epicycle; the location of the epicycle centre in longitude, measured as an arc
at E from either ♈ or A (those arcs
are known as mean longitude and mean centre, respectively); and the arc of the motion
of the planet around the
epicycle (mean anomaly), measured from the mean epicyclic apogee (a point on the epicycle
diametrically opposite to
E). The diagram below (left) shows this (each planet has a different D, E, and A).|
Because the relative sizes of the deferent circle and epicycle varied between planets,
early equatoria
essentially consisted of separate instruments for each planet. However, the Peterhouse
design accommodates models for
all planets in a single instrument, as the diagram above (right) shows. The ecliptic
is marked on a wooden disc
(indicated by the green circle). The red deferent circle, on which is located the
epicycle centre, is reduced to the
radius of a large brass ring. The centre of that ring is the epicycle centre. One
end of a rotating rule (the “label”)
is attached to a bar running across the ring; on it are marked the radii of the planets’
epicycles. As the label
turns, the planets’ epicycles are traced out.|
To measure the planet’s longitude on the epicycle, the treatise instructs the user
to mark out the mean
longitude (the treatise calls this the “mean motus”) using a black thread from W;
this is translated to E using a
parallel white thread. The rim of the brass epicycle is fixed to D and the epicycle
is rotated so its centre is under
the white thread. The mean anomaly (“mean argument” in the treatise) is marked out
by turning the label anticlockwise
from the mean epicyclic apogee (where the white thread crosses the far rim of the
epicycle). The black thread is then
moved to the planet’s mark on the label; the planet’s longitude (“verrey [true] place”)
can be read where the thread
crosses the scale on the wooden disc.|
The longitudes of the Sun, Moon and Mercury can be computed using similar methods.
A scale on one half
of the wooden disc allows the Moon’s latitude to be computed; this is sinusoidally
related to its elongation from its
nodes (where its orbit intersects the ecliptic). On the other half of the disc is
a scale that was intended for
computation of the accession and recession of the eighth sphere, which was one component
of precession (by which the
apogees of the Sun and planets moved against the background of fixed stars). It is
clear how this scale would have
worked, but it is not fully explained and would not have given as good results as
the lunar latitude scale.|
The tables which comprise the bulk of the codex may be divided into three parts.
First (ff. 1r-13v) are a set in Hand C, giving the information necessary for the use of the equatorium
as described above: annual and daily values for the mean longitudes and mean anomalies.
Next are a set in Hand S
(ff. 14r-62r) containing much of the same information in calendar form, as well
as tables to compute planetary longitudes and latitudes independently from the equatorium.
Finally, a further set of
tables in Hand C (ff. 62v-71r) includes information of general astronomical and
astrological interest, some of which is suited to use with the equatorium. Notes and
updated values in the tables
testify to their continued interest for the author of the treatise after their composition.|
| Seb Falk| November 2014|
,
Equatorie of the Planetis
Language(s): Middle English, Latin
Physical Description
Form: codex
Support:
Parchment
Extent: i + 78 + ii fols; part of early thick parchment wrapper preserved as folded endleaf;
one modern blank leaf at
each end. | First nine quires:
Dimensions (leaf):
365 × 275 mm.
Last quire:
Dimensions (leaf):
335 × 245 mm.
Size of written area of both table and text pages very variable; largest written
area on page of
text (f. 71v):
Dimensions (written):
305 × 240 mm.
Collation
The MS consists of ten quires as follows:
- 1 modern paper flyleaf (unnumbered)
- Quire 14 (fols 1-4)
- Quire 214, wants leaves 8-11, 13 (fols 5-13)
- Quire 312 (fols 14-25)
- Quire 412, wants leaf 7 (fols 26-36)
- Quires 5-612 (fols 37-60)
- Quire 74 (fols 61-64)
- Quire 88, wants leaves 1-2 (fols 65-70)
- Quires 9-104 (fols 71-78)
- Folded endleaf (early wrapper, unnumbered)
- 1 modern paper flyleaf (unnumbered)
Layout
Hand S's leaves (fols 14r-62r) are pricked and ruled (in both brown ink and
drypoint) to accommodate tables with variable contents. John Westwyk's leaves (fols
1r-13v and 62v-78v) are not pricked; his tables ruled
variously in drypoint and ink (brown and red), to accommodate contents. His text written
in long lines across
unruled pages with no right-hand margin. Most, but not all, pages of text have three-quarter
frames. 2º fol.
Secundo Folio: Medius motus
Hand(s)
John Westwyk (fols 1r-13v and 62v-78v): current Anglicana bookhand. Also annotations (some in cipher) on tables by Hand S on fols 14r-17r, 20r, 21r-22r, 23r-23v, 25r-25v, 26r, 27r-27v, 29r, 30r-32v, 36r-36v, 38v, 45r, 48r, 51r, 54v-55r and 58v)
Hand S (tables, fols 14r-62r): Anglicana bookhand
Punctuation: Most frequent are the wedge paragraphus and the single virgule. Double virgules, and a point followed by a single virgule also occur. Carets for insertions. Numerals in the text usually enclosed by raised points
Decoration
Horoscope with accompanying Latin text on fol. 64v. Equatorium figures on fols 73v (one) and 74r (two)
Binding
New binding by John P. Gray, Cambridge c. 1952-1955 after separation from what is now MS 75.II. Full pale brown goatskin. Cloth slipcase. Previous binding's coverskin and pasteboards used to rebind MS 75.II
History
Origin:
c. 1393
; England
Provenance and Acquisition
Perhaps to be identified with an item recorded as an addition to the Peterhouse library catalogue of 24 December 1418, written in the hand of Roger Marchall in 1472: see CBMLC 10, UC48.389 and Voigts (1995), pp. 285-86.
Certainly at Peterhouse by c. 1542, when it was described by John Leland: see CBMLC 10, UC49.44). Entered in a college booklist compiled between 1589 and 1593 (Ward Library MS 400, p. 12).
Additional Information
Record Sources
Availability
Researchers should note that Peterhouse's western European medieval manuscripts are housed at Cambridge University Library. Scholars who wish to consult Peterhouse manuscripts should contact the Special Collections Reading Room to arrange their visit; all University Library admissions procedures will apply. For information on eligibility and admissions procedures, see Joining the Library. For further enquiries, and to confirm the availability of the manuscript, please contact the Special Collections Reading Room.
Bibliography
-
A descriptive catalogue of the manuscripts in the library of Peterhouse, James, M. R. (Cambridge, Cambridge University Press, 1899)
Calendar of Papal Registers Relating To Great Britain and Ireland. Volume 5, 1398-1404, Bliss, W. H.Twemlow, J. A. (London, HMSO, 1904)
The Equatorie of the Planetis, (Cambridge,, Cambridge University Press, 1955)
Kalenderes Enlumyned Ben They: Some Astronomical Themes in Chaucer The Review of English
Studies, North, J. D. (20, 129-154, 257-83, 418-44, 1969, http://www.jstor.org/stable/512545)
Les instruments de la théorie des planètes selon Ptolémée: équatoires et horlogerie
planétaire du
XIIIe au XVIe siècle Collection des travaux de l'Académie internationale des sciences, Poulle, Emmanuel (Genève; Paris, Droz; H. Champion, 1980)
Chaucer's universe, North, John David (Oxford, Clarendon Press, 1988)
Catalogue of Dated and Datable Manuscripts c. 737-1600 in Cambridge Libraries, Robinson, P.R. (Cambridge, D.S. Brewer, 1988)
Chaucer's spelling reconsidered English Manuscript Studies: 1100-1700, Benson, Larry (3, 1-28, 1992)
The vocabulary of <hi rend="italics">The Equatorie of the Planetis</hi> and the
question of authorship English Manuscript Studies: 1100-1700, Partridge, Stephen (3, 29-37, 1992)
The authorship of the <hi rend="italics">Equatorie of the planetis</hi> Chaucer studies, Rand Schmidt, Kari Anne (Cambridge, D.S. Brewer, 1993)
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2002)
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Data Service, Riddy, Felicity (2008, https://archaeologydataservice.ac.uk/archives/view/ump_ahrc_2008/index.cfm)
The Library of Peterhouse, Cambridge and the Problem of the Spatial Arrangement of
Knowledge
during the Sixteenth and Seventeenth Centuries Museum, Bibliothek, Stadtraum: Räumliche
Wissenordnungen 1600-1900, Mandelbrote, Scott (Berlin, 2010)
The Scholar as Craftsman: Derek de Solla Price and the Reconstruction of a Medieval
Instrument Notes and Records of the Royal Society, Falk, Sebastian (68, 111-134, 2014)
Scribal Correction and Literary Craft: English Manuscripts, 1375-1510 Cambridge Studies
in Medieval Literature, Wakelin, Daniel (Cambridge, University Press, 2014)
The Authorship of The <hi rend="italics">Equatorie of the planetis</hi>
Revisited Studia neophilologica, Rand, Kari Anne (87, 1, 15–35, 2015)
John Holbroke, the Tables of Cambridge, and the “true length of the year”: a forgotten
episode in
fifteenth-century astronomy Archive for History of Exact Sciences, Nothaft, C. Philipp E. (72, 1, 63-88, 2018, https://doi.org/10.1007/s00407-017-0200-0)
Digital Images
Abbreviations
View list of abbreviations and editorial conventions.
