Previous walks      Weather     Links    
Search Dartmoor CAM

#htmlcaption #htmlcaption #htmlcaption #htmlcaption #htmlcaption #htmlcaption #htmlcaption #htmlcaption #htmlcaption #htmlcaption

 

 

 

The Merrivale stone rows solar calendar

Back to the main Merrivale page - CLICK HERE.

Photographs taken around the winter solstice etc. - CLICK HERE

Explanation about the how the stone rows work as a sun calendar - CLICK HERE

Summary photographs - CLICK HERE

 

While being very elegant in its simplicity, it is also sophisticated in its complexity!

 

Summary

The two double stone rows at Merrivale are oriented not quite east-west but at 85.  They are more or less parallel, about 50 metres apart. The northern row is 183 metres in length whereas the southern row is 263.5 metres. about 80 metres longer.  This overlaps the northern row, but more so at the west end.  A line drawn through the west end, northern row, and the east end, southern row, extends to the positions of sunrise and sunset at the equinoxes in March and September, when day and night are of equal length. Similar lines extended beyond the east ends and the west ends of the two rows point to the sunrise and sunset positions of the solstices in December (mid-winter) and June (mid-summer).  These indicate very simply the most important dates in the yearly cycle for Bronze Age farmers, although they might have had the ability to use this calendar on a finer scale.  

 

Sources

 

There is an old saying - If it looks like a duck, swims like a duck and quacks like a duck - then it's a duck!  (Duck test - Wikipedia)

Something similar can be said about the Merrivale stone rows - "If they are conceived as a solar calendar, constructed as a solar calendar and function as a solar calendar -  then they are a solar calendar!"

The ends of the stone rows align with the solstice sunrises and sunsets and the diagonal between the ends of the two rows aligns with the equinoctial sun events.  This alone suggests the function of the rows as a solar calendar, but the rows are more sophisticated than they first appear.

A calendar would have been of great importance in the Bronze Age, 2,500 to about 800 BC.  This was when farming came to prominence on Dartmoor and knowing when to plant crops would have been critical for survival. Dartmoor was a populous area until the climate changed around 700-800 BC and the Bronze Age ended..

A brief history:

 

Merrivale stone rows - redrawn with modifications and additions from Jack Walker, 2005, Dartmoor Sun, Halsgrove Discover Series, Halsgrove Publishing, Tiverton, Devon, pages 70 & 103.

 

The rows work as a simple line-of-sight system for observing direct alignments of the sun rising each morning, and this system will be described first.

 

Observation of sunrise - by direct line-of-sight

The easiest explanation is to start with the winter solstice, around Dec. 21.  If you stand at the east blocking stone of the northern row, the sun rises over the east blocking stone of the southern row.  A few days later, to repeat this phenomenon - of sunrise over the blocking stone, you must move a few stones westward along the northern row, as the sun begins its journey north.  This continues through Jan, Feb. and March until the equinox on March 21, when you are standing at the west end of the northern row.  This is the result of the rows not being aligned 90 east-west but are slightly offset at 85  There is then a hiatus, because of the arrangement of the rows.  About Apr. 6,the rising sun is in line with the southern row.  From about  Apr. 17, the sun rises over the east blocking stone of the northern row.  Now, all following observations (after about Apr. 17) can be made from the west end blocking stone, southern row) without moving, watching the sunrise progress westwards along the northern row until it rises over the west end (small blocking stone?) of the northern row on June 21. 

Then, for the last six months of the year, the system works in reverse.  From Jun 21, the observer can stay at the west blocking stone of the southern row, watching the sunrises creep back eastwards along the northern row until a later hiatus / crossover date, Oct. 19.  However, the Sep. 21 equinox sunrise can be observed from the west blocking stone, northern row, over the east blocking stone of the southern row, as above on Mar. 21.  At the equinox, the observer can move to the west blocking stone of the northern row and move eastwards to observe the sunrise over the east blocking stone of the southern row until winter solstice again, Dec. 21.

 


Image used by kind permission of Torsten Hoffmann, SunCalc.

SunCalc image showing the minute of sunrise on Dec. 21, winter solstice, at the east end of Merrivale stone rows. The red pointer, the "centre" of the display is placed over the blocking stone of the southern row and as the sun rises, the stone casts its shadow straight towards the blocking stone of the northern row (in the white circle). 

 

Dartmoor CAM movie. TIPS .....

  • once viewing, make movie viewer "Full Screen"

  • can click the loop or "continuous play" icon (if there is one)

  • press F11 to make more "Full Screen", remembering to press it again to regain Normal Screen.

An animation of sunset on the summer solstice, Jun. 21, at the east end of the Merrivale stone rows


.Image used by kind permission of Torsten Hoffmann, SunCalc.

Click the photo to download

File size: 15 MB.
Length 1:35 minutes

 

 

Simplified explanation of how the calendar works for direct observation of sunrise

 

 

Starting with mid-winter sunrise, the observer stands at the eastern blocking stone of the northern row and notes the sun rising over the east blocking stone of the southern row. On following days, the sun will rise further north on the horizon and the observer must move westwards along the northern row to keep the observation of sunrise over the southern row blocking stone.

 

 

Around the spring equinox, Mar. 21, the observer will be at the extreme west end of the northern row, observing the sun rise over the same blocking stone in the southern row.  There is a hiatus until about Apr. 6 when the rising sun is in line with the southern row.  From about  Apr. 17, the sun rises over the east blocking stone of the northern row.

 

 

 

After about Apr. 17, the sunrise can be followed westward along the northern row until Jun. 21, on the longest day, it is observed rising over the west end blocking stone of the norethern row when observed from the west end blocking stone of the southern row.  The system then reverses back to Dec. 21.

Thus, you have a simple system for directly seeing or forecasting the sun rise almost each day of the year .....

The sun rises for the first quarter of the year, over the east blocking stone of the southern row while you move west along the northern row; and for the second quarter you watch it from the west blocking stone of the southern row as it rises moving westwards along the northern row until summer solstice, Jun. 21, when it rises over the west blocking stone of the northern row.  After solstice, the system works in reverse.

Forecasting future dates / events might be done using the spaces between the stones in the row, see the extra data at the bottom of this page.

 

 

The chart above was prepared by plotting shadows cast from the southern row east blocking stone toward the northern row, using SunCalc.net and Suncalc.org from Dec. 21 to Mar. 21 at weekly intervals.  The results i.e. locations along the row, can be reversed for Apr. to Jun, and then used again for Jul. to Sep, and finally reversed for Oct-Dec.  The course of sunrise and sunset traversing the ends of the rows is a dynamic situation.  As the sun event reaches the end of the row, the difference in the observation location along the row speeds up - there is no simple linear scale.

 

1 2 3 4 5 6 7 8 9 10 11 12 13
1 - Dec 21 2 - Dec 28 3 - Jan 4 4 - Jan 11 5 - Jan 18 6 - Jan 25 7 - Feb 1 8 - Feb 8 9 - Feb 15 10 - Feb 22 11 - Mar 1 12 - Mar 8 13 Mar 15
26 - Jun 14 25 - Jun 7 24 - May 31 23 - May 24 22 - May 17 21 - May 10 20 - May 3 19 - Apr 26 18 - Apr 19 17 - Apr 12 16 - Apr 5 15 - Mar 29 14 - Mar 22
27 - Jun 21 28 - Jun 28 29 - Jul 5 30 - Jul 12 31 - Jul 19 32 - Jul 26 33 - Aug 2 34 - Aug 9 35 - Aug 16 36 - Aug 23 37 - Aug 30 38 - Sep6 39 - Sep 13
52 - Dec 13 51 - Dec 6 50 - Nov 29 49 - Nov 22 48 - Nov 15 47 - Nov 8 46 - Nov 1 45 - Oct 25 44 - Oct 18 43 - Oct 11 42 - Oct 4 41 - Sep 27 40 - Sep 20

 

The table above shows the 13 weeks in each quarter between equinoxes and solstices and the distance points along the northern row where the sun events may be observed from to see them over the appropriate blocking stone. Note the order/sequence of the numbered cells: left to right, right to left, left to  right and finally right to left.  The weeks containing the solstices and equinoxes are marled in yellow. 

 

If the distance scale is plotted logarithmically, we see an "almost straight line" .....

 

 

 


 

 

Observation of sunrise - by shadow-casting

Instead of directly observing the sun rise through the year over specific small stones in the distance, the system can be used in reverse to the above system, by shadow-casting.  In this case. at winter solstice, Dec. 21, you would stand at the east blocking stone of the southern row and as the sun rises, your shadow would suddenly appear pointing straight at the east blocking stone of the northern row.  You would stand here for each sunrise to Mar. 21 when your shadow would point to the west blocking stone of the northern row.  After the March equinox, you would move to the east blocking stone of the northern row, and move westwards along the row while casting your shadow on the west blocking stone of the southern row, until summer solstice, Jun. 21, when your shadow would fall between the two west blocking stones. The system then works in reverse back to Dec. 21.

Long shadows are much easier to see sometimes compared to seeing small stones in the distance.

 


Image used by kind permission of Torsten Hoffmann, SunCalc.

SunCalc image showing the minute of sunset on Dec. 21, winter solstice, at the west end of Merrivale stone rows. The red pointer, the "centre" of the display is placed over the blocking stone of the southern row and as the sun sets, the stone casts its shadow straight towards the blocking stone of the northern row (in the white circle).  This northern row terminal stone is quite diminutive and perhaps a real blocking stone has been removed.

 


Image used by kind permission of Torsten Hoffmann, SunCalc.

SunCalc image showing the minute of sunrise on Jun. 21, summer solstice, at the west end of Merrivale stone rows. The red pointer, the "centre" of the display is placed over the west blocking stone of the northern row and as the sun sets, the stone or an observer casts a shadow straight towards the blocking stone of the southern row (in the white circle).  This northern row terminal stone is quite diminutive and perhaps a real blocking stone has been removed.

 

 


 

Having described the two systems above, we can double the complexity again by saying that the two systems can be used in reverse for observing sunset.

 

Observation of sunset - by direct line-of-sight

Starting with winter solstice, Dec. 21, the observer stands at the west blocking stone, northern row, and sees the sun set over the west blocking stone, southern row.

Then, to maintain sunsets over the blocking stone, the observer must move eastwards along the northern row until the crossover date of Feb. 23.  This method seems to have a short-coming between Feb. 23 and the Mar.21 equinox.  It is possible that Row 3, the small additional stone row on the south side of the southern row, came into play but precisely how cannot be said  At equinox,  the sun sets over the west blocking stone of the northern row when observed from the east blocking stone of the southern row.  After the equinox, the observer stays at the east blocking stone of the southern row and watches the sunsets move eastward along the northern row until it sets over the east end blocking stone on Jun. 21. Then the system reverses back to Dec. 21.

 


Image used by kind permission of Torsten Hoffmann, SunCalc.

SunCalc image showing the minute of sunrise on Sep. 21, the equinox, at the Merrivale stone rows. The red pointer, the "centre" of the display, is placed in a position where the east and west lines of the display lie in an near-perfect east-west alignment, in agreement with a compass.  This shows the non-east-west alignment of the double stone rows, which are orientated at about 85.   The ends of the two rows are marked by white circles around their terminal or blocking stones. 

 

 

Observation of sunset - by shadow-casting

Starting with winter solstice, Dec. 21, the observer stands at the west blocking stone, southern row, and the shadow is cast to the west blocking stone of the northern row.  Through Jan. to Mar. the observer stays at this blocking stone and the sunset shadow moves eastwards along the northern row.  Again, there is a hiatus between Feb. 23 and Mar. 21. After the equinox on Mar. 21, the observer moves to the west blocking stone of the northern row and casts a shadow to the east blocking stone, southern row.  He moves eastwards along the northern row to maintain casting a shadow to the east blocking stone, southern row until reaching the east blocking stone (northern row) at summer solstice on Jun. 21.  After Jun. 21, the observer moves back westwards along the northern row to maintain casting a shadow on the east blocking stone of the southern row, until Sep. 23 equinox.  There is another hiatus until Oct. 19, when there is an alignment between the west blocking stone, southern row, and east blocking stone, northern row.  After this date. the observer stands at the west blocking stone, southern row, and watches the shadow cast towards the east end blocking stone, northern row, move westwards along the northern row until it is cast directly to the west blocking stone (northern row) from the west blocking stone (southern row) at the Dec. 21 solstice.

 

In conclusion, there are actually four calendar systems-in-one in the rows:

 

1 Sunrise direct line-of-sight
2 ditto shadow casting
3 Sunset direct line-of-sight
4 ditto shadow casting

 

 


Footnote

I was originally inspired to think particularly about Merrivale after reading Jack Walker's book, Dartmoor Sun, published in 2005 by Halsgrove Publishing.  I bought it in about 2010 and read it avidly.  Since I wrote this page I have looked at it again and, I see now that he has more use for the southern row than I have given it - I only used the two end blocking stones!  I have concentrated on the northern row because it seemed simpler and also I didn't really understand some aspects of the swap-over between the rows involving the equinoxes.  As the publisher says in the Foreward to the book, Jack is an engineer and brought an engineer's mind to the problem.  I was a biologist who spend his career in  electron microscopy and x-ray microanalysis looking ever-closer into things.  I sometimes took a long time to step back and see the wood for the trees.  The same has happened here - I was looking for the organelle structure within the cells and neglected to ;look at the forest.  However, it seems to work either way, and with both direct observation and the casting of long shadows!  I can only marvel that Bronze Age people, over 4,000 years ago, were capable of such concepts, planning and execution.

Dr Keith Ryan, BSc, PhD, CBiol, FRSB, FRMS

 


 

Some additional data

How to measure the days?

  Length
(metres)
Total no. of stones
some fallen, some buried
Distance between stones
along the row (metres)
"No. of stones = 1 day"
Average "guesstimate"
Northern row 183 204 1.6-1.9 m 2.25
Southern row 263.5 281 1.2-2.9 m ---

 

This data, except for "No. of stones = 1 day" from Jeremy Butler, 1994, Dartmoor Atlas of Antiquities  Vol. 3 - The South-West, Stone rows, page 204.

The initial concept here was that perhaps it was possible to measure or predict "dates" along the northern row by counting the stones using a simple linear scale, such as: when marking days by the calendar, the progression from e.g. winter solstice to spring equinox is approx. 90 days. This might have been marked by the observer moving along the northern row: with its 204 stones: this equates to 2 metres or 2.25 stones per day.   No such luck. Now, this can be estimated from the first chart and table in the text above.

 

Solar periods: solstice and equinox dates for (2016) 2017 highlighted below

For Greenwich Meantime 2017

(Dec 21) - Dec 31 11 days
Jan 1 - Jan 31 31
Feb 1 - Feb 28 28
Mar 1 - Mar 19 20
  89 days
Mar 20 - Mar 31 11
Apr 1 - Apr 30 30
May 1 - May 31 31
Jun 1 - Jun 20 20
  92 days
Jun 21 - Jun 30 10
Jul 1 - Jul 31 31
Aug 1 - Aug 31 31
Sep 1 - Sep 21 21
  93 days
Sep 22 - Sep 30 9
Oct 1 - Oct 31 31
Nov 1 - Nov 30 30
Dec 1 - Dec 20 21
  91 days
Total 365 days

 

 

 

All photographs on this web site are copyright © Keith Ryan.
All rights reserved - please email for permissions