History Section
The History Section
La Section d'l'Histouaithe
A brief description of
The Sundial
at
The Parish Church of St Peter
In the Island of Jersey
Introduction
The Old Sundial
The old sundial was designed to face due south and was set in the niche, above the window in the south transept. As the wall does not face due south the western end of the dial was set back in the recess.
We do not know when the old dial was made. In 1855 the south transept gable was rebuilt. The sundial may have been new when it was placed in the niche at that time, or possibly it had already seen years of service.
The dial was carved on a pale limestone slab. This had suffered erosion on its eastern side. Parts of the carving had almost disappeared and what remained was obscured by lichen. On the western side, sheltered within the niche, the lettering was fresh. The wrought iron gnomon (shadow-casting bar) had been weakened by rust and was distorted. Where the lower part of the gnomon was secured through the stone, the rusting had split the lower part of the slab and, when the dial was removed, a large section disintegrated.
The old sundial has been presented to the Jersey Heritage Trust.
The New Sundial
The new sundial is made of Welsh slate from Snowdonia. The gnomon is of stainless steel with a 'golden' ball that casts a shadow on a curved line to mark the feast day of St Peter. The style of Roman numerals and the general layout of the lines are very similar to the old dial. The gnomon also follows the general shape with a hoop support, although it is less ornate than the original.
The major difference is that the new dial fits snugly in its niche. This has been achieved by designing the dial for this particular position and orientation. It is a Vertical Declining Sundial.
Telling the Time
The shadow of the sloping part of the gnomon indicates the local Sun time. The shadow is quite wide and you should estimate where the centre of the shadow falls in relation to the nearest hour, half or quarter hour line. In this way it is possible to find the time to within a few minutes.
That would have been sufficient for our ancestors but most people today need to know 'clock time' rather than local Sun time.
Adjusting for Clock Time
The Earth spins on its axis with great precision. Although there is some variation, only sophisticated clocks can detect it. Unfortunately, if we measure the rotation of the earth by reference to the Sun we have a problem. The Earth follows an elliptical path around the Sun and moves faster on certain parts of this curve than on others. A further complication is the tilt of the Earth's axis. Because of this tilt we have our seasons and an apparent irregularity of the Sun's time keeping.
In the 17th century the first calculation of the adjustment needed to correct these differences was made and it was called, in the terminology of those days, the Equation of Time.
A further adjustment is needed to convert to clock time. Allowing for the Equation of Time correction, we can assume that it takes precisely 24 hours for the Earth to spin round until the sun is in the same place in the sky. Geographers and navigators divide the Earth into 360o of longitude. In one hour the Earth moves through 15 o so the Sun time is one hour later than at a place 15 o to your East. Every degree is equivalent to 4 minutes of time and a minute of longitude is 4 seconds of time. This is the principle used by navigators to find their position at sea, before the advent of global positioning satellites. The longitude of St Peter's Church is 2o 11' west of Greenwich. This works out at 8 minutes and 44 seconds behind Greenwich time. It may disappoint St Peter's Parishioners to know that the inhabitants of St Catherine's, at 2o 01', are 40 seconds ahead, in Sun time
The adjustments for the Equation of Time and the Longitude have been combined into a graph, which is shown on a plaque fixed to the wall by the sundial. Details of the plaque are reproduced below A table presenting the same information, to the nearest minute, is shown below. To find clock time, take the local Sun time from the dial then find today's date on the table, or the graph, and add, or deduct, the number of minutes shown. An hour should be added when British Summer Time applies.
Adjustment for Equation of Time & Longitude
| Minutes | Minutes | Minutes | Minutes | Minutes | Minutes | |||||||||||
| Jan | Mar | May | Aug | Oct | Dec | |||||||||||
| 1-3 | +13 | 1-3 | +21 | 1-3 | +6 | 1-6 | +15 | 1-3 | -2 | 1-2 | -2 | |||||
| 4-5 | +14 | 4-7 | +20 | 4-23 | +5 | 7-13 | +14 | 4-6 | -3 | 3-4 | -1 | |||||
| 6-7 | +15 | 8-11 | +19 | 24-31 | +6 | 14-17 | +13 | 7-10 | -4 | 5-7 | 0 | |||||
| 8-10 | +16 | 12-15 | +18 | Jun | 18-22 | +12 | 11-14 | -5 | 8-9 | +1 | ||||||
| 11-12 | +17 | 16-18 | +17 | 1-6 | +7 | 23-25 | +11 | 15-19 | -6 | 10-11 | +2 | |||||
| 13-15 | +18 | 19-22 | +16 | 7-11 | +8 | 26-29 | +10 | 20-27 | -7 | 12-13 | +3 | |||||
| 16-18 | +19 | 23-25 | +15 | 12-16 | +9 | 30-31 | +9 | 28-31 | -8 | 14-15 | +4 | |||||
| 19-22 | +20 | 26-28 | +14 | 17-20 | +10 | Sep | Nov | 16-17 | +5 | |||||||
| 23-26 | +21 | 29-31 | +13 | 21-25 | +11 | 1 | +9 | 1-8 | -8 | 18-19 | +6 | |||||
| 27-31 | +22 | Apr | 26-30 | +12 | 2-4 | +8 | 9-15 | -7 | 20-21 | +7 | ||||||
| Feb | 1-4 | +12 | Jul | 5-7 | +7 | 16-20 | -6 | 22-23 | +8 | |||||||
| 1 | +22 | 5-7 | +11 | 1-5 | +13 | 8-10 | +6 | 21-23 | -5 | 24-26 | +9 | |||||
| 2-19 | +23 | 8-11 | +10 | 6-13 | +14 | 11-13 | +5 | 24-27 | -4 | 27-28 | +10 | |||||
| 20-26 | +22 | 12-15 | +9 | 14-31 | +15 | 14-15 | +4 | 28-29 | -3 | 29-30 | +11 | |||||
| 27-28 | +21 | 16-20 | +8 | 16-18 | +3 | 30 | -2 | 31 | +12 | |||||||
| 21-25 | +7 | 19-21 | +2 | |||||||||||||
| 26-30 | +6 | 22-24 | +1 | |||||||||||||
| 25-27 | 0 | |||||||||||||||
| 28-30 | -1 | |||||||||||||||
Commemoration of St Peter.
As already mentioned, the axis of the Earth is tilted. In summer the Sun is higher in the sky, at any particular time, and daylight lasts longer. Taking advantage of this, the sundial has a line that will be followed by the shadow of the golden ball on the gnomon between 8:15 am and 2:30 pm local Sun time (09:00 to 15:15 British Summer Time). The line has been drawn to match the height of the Sun on 29 June – St Peter's Day. As the height of the Sun changes gradually the shadow will forecast the festival and will remain as a reminder for a few days afterwards.
There appears to be no other public sundial in Jersey that includes such a declination line.
Harriet James.
The sundial was designed and carved by Harriet James. Harriet is one of a small number of skilled craftsmen in the United Kingdom who specialise in the construction of sundials. From her workshop in Wiltshire, Harriet has provided vertical and horizontal sundials carved in various types of stone for locations across the UK. This is the most southerly dial she has made.
Other Jersey Parish Church Sundials
.
Unless otherwise stated the sundials are vertical south facing dials and are to be found on the south sides of their churches.
| St Brelade | A limestone dial dated 1837 with an Equation of Time indicator for each sign of the zodiac. Motto, from Psalm 144 v 4, 'L'HOMME EST SEMBLABLE À LA VANITÉ, SES JOURS SONT COMME UNE OMBRE QUE PASSE' |
| St Clement | A vertical declining dial in slate. Removed from the church some years ago and now on the wall in the Rectory garden. Two mottoes: 'La dernière est inconnue', 'Nos jours passent comme une ombre' |
| St Lawrence | A semi-circular limestone dial, possibly 17th century. Found inside the church in the 1890s, given to Société Jersiaise in 1933 and reinstalled in the church wall in June 1978. A rededication service was held on 7 January 1979. |
| St Martin | A white marble dial made around 1987 to replace a slate dial that had disintegrated. The original dial was the gift of George Bandinel, Churchwarden, in 1736. The inscription carved in the granite frame around the dial: 'Don De G B Surveillant 1736'. |
| St Mary | A pale grey/white marble dial dated 1763 with the motto; 'UT UMBRA SIC VITA'. In 1762 Thomas Nicolle was given permission to alter a pew, following a dispute, and part of the settlement was that he should arrange for a sundial to be made on a piece of marble. |
| St Saviour | A vertical declining dial in granite, installed in the early part of the 20th century. The motto: 'MY TIME IS IN THY HAND' |
Technical Matters
St Peter's Church is at latitude 49o 12.7' north, longitude 2o 11' west. Grid reference 596516
The dial is carved on a slab of Welsh slate from Snowdonia. It is 730 mm square and 45 mm thick.
The gnomon is made from stainless steel rod with a circular cross section, 10 mm diameter. It is secured with threaded nuts on the back of the slab.
The design takes into account the declination of the wall 8.88o east of south and the latitude of 49o 12.7' north
The gnomon makes an angle of 40.2o with the face of the dial and the substyle angle with the vertical is 7.6o.
A 30 mm sphere on the gnomon is of phosphor-bronze and was electro-plated with nickel and then gold. This is a 'nodus', which casts a shadow that follows the curved declination line on 29 June: St Peter's Day. Crossed keys, the traditional symbol of St Peter and the badge of the Parish, identify this line.
The hours are numbered with roman numerals from VI to V, with four shown as IIII. The numbers are upright. A cross represents noon. The numerals are 67 mm high.
The hour lines, with a V profile, are 10 mm wide and extend from the border to a semicircular space centred on the origin of the gnomon. The noon line extends right up to the origin of the gnomon. The half hours are marked with shorter lines, 5 mm wide and the quarter hour marks are confined to the width of the border.
At the top of the dial is the date, 2004, the year of construction and installation.
All the straight lines on the sundial are picked out in platinum leaf. The roman numerals and the date are in gold leaf and the declination line and crossed keys are in 'red' gold leaf.
The sundial was fitted and secured in the granite-framed niche by Mr Harry Tumblety the builder. Mr Tumblety is a specialist in ecclesiastical and historical conservation work.
