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Megalithic art studies by M. Brennan

Alignments

Calendar

• Division of year in 12 is looking at moon, while dividing it by 8 is looking at sun.
• 62 lunar synodic months is almost equal to 5 solar tropical years
• 99 lunar synodic months is almost equal to 8 solar tropical years (Octaëteris cycle) and 5 Venus synodic years

Symbols and motifs

Classification

Interesting issues

• After spring equinox interest shifts to lunar observation
• The 17^th moon phase projects a light beam in mound (page 152).
• Light reflecting on other stones is used to emphasis other art.
• "Many of the motifs found in the art are cosmograms or graphic models of the structure of time and space."
• I don't kow if the horns of the solstices provide a nice explanation of a loosely and tightly wound spiral (see also remark).
  
  
  (horizontal: time of day [hour], vertical: length of shadow [m] in North direction)
  
  
  A nice art piece that made the horns visible is from Charles Ross, below are some cut and pastes from this link (I assume Ross used a gnomon that was directed to sun at noon on equinox day):
  sun burnts around winter solstice:
  sun burnts around summer solstice:
  A nice relation with equinox is here.
  
• The sun moves in a clockwise spiral and the stars revolve anti-clockwise (page 190). I think Ross put all the single day burns in one line: tail to head and positioning them in such a way that the form of the 366 burns makes a smooth line. That makes indeed a double spiral (left picture). After thinking about this, I tried to see if that thought was correct and on this web page it tells: "Ross also discovered that when laid end to end, the solar burns trace a double spiral.". I don't know if this is indeed a good explanation for how neolithic people might have done it. I agree it is a nice and creative form made by Ross. But I am not really overwelmed/convinced by Brennan's interpretation.
• The moon loops cross the ecliptic in an anti-clockwise motion.
• Evolution with regard to number of spirals close to each other: One spirals at Dowth, two spirals at Knowth and three spirals at Newgrange.

Compositions

• sundials
• rows of eleven zigzags (days of sun in Newgrange chamber)
• half/full year (6/12 arcs and circle, 6/12 zigzags, 6/12 waves in serpentiforms, 4/8/12 triangles)
• nine zigzag/waves: half of lunar nodal cycle
• 19 arcs/zigzags: Metonic cycle
• 18 arcs/zigzags: Saros cycle

Some remarks

• page 70
Mound L and Mound K are interchanged in the picture
• page 72, 118, 126 and 192
The 'True North' direction is wrongly copied from O'Kelly. This makes some of the proposed alignments not fully correct.
• Page 72 and 193
The rendering of K1 at Newgrange is partially wrong. The most right double spiral has been rendered as negative (compare it with photograph on page 29).

• Page 72
  The standing stone numbering is different then the great circle stone numbering of O'Kelly. See here for a translation.
  
• page 73 and 177
The rendering of K52 is a little bit to artistic/smoothed. E.g. the wedges around the three cup marks not always exist.
• page 78
  Don't understand the text belonging got the picture. Which basin in the floor of the chamber is meant (the one in the recess or in the centre of the chamber?). I only see the one in the recess.
• page 101
  It looks that GC1 is casting a shadow at wintersolstice on K-1 and GC-1 provides a shadow on K-93. But looking at for instance picture page 126, I don't think this is correct!
  If GC1 gives a shadow on K-1, than GC-2 could perhaps give a shadow on K-93 (GC-1 could do it perhaps on K-96)...  So this really needs some real observations!!!
  
• page 102
• The map of Knowth is wrong. e.g. the passages are not directed due east and west. It is assumed that it was sourced in early times [1982] from Eogan (like Thomas).
• The south part of the map is quite messed up. Stones between and including S0 until SE28, are positioned much more to the west (S0 is equivalent to K30, and thus more south-west!). A mapping between Brennan's numbering and Eogan's is here.
• page 109
  The art on stone 7 could be very well be natural holes in the stone (there are tens of them).
  
• page 111
  The art in Cairn H has different locations then depicted in Brennan (stones 2 and 3 in page 111, 1983), they should be a stone closer to the entrance (see Shee Twohig (R2 and L2 in fig. 215, 1981)).
  
• page 116
  The plan in Brennan is correct (expect perhaps there is no southern recess). The plan in Shee Twohig  (fig. 231, 1981) is not correct.
• page 136
There are 29/30 days in the synodic month, not 28 days.
• page 137
This figure is never referred to (it shows the periodicy of the lunar perturbation, 173 days, half eclipse year).
• page 148
Cairn T, stone 20 should be stone 19
• page 158 and 159
  The drawing of Knowth NE4 (K7) is not correct. It should have 4 dots instead of 3 dots on the outside.
  
• page 162
Cairn T, stone 1 should be stone L1
• page 169
The rendering of the roofstone of right recess at Newgrange is wrong.
• page 190
The horns of the solstice picture should be changed a little bit. The distance between summer solstice and equinox line is smaller than the distance between the equinox and winter solstice line (Waugh [1973], page 173). See also picture above.

• page 194
The triple double spiral depicted is not the one in the chamber of Newgrange, but the one on K1.

Questions to author

• Is the number of eleven days that the sun light is in the chamber of Newgrange, really witnessed?
• Why not show (page 137) the lunar nodal cycle? So that minor and major lunar standstill limits are explained.
• Why is number 27 days related to lunar synodic month (27 visible phases, page 137), why not to the lunar tropical month (which is comparable witnessable on horizon as the sun's path: solar tropical year)?
• Can you explain the relation with lunar perturbation and the 5 year (62 months) cycle (figure page 145)?
• Why (page 186) is the sidereal (stellar) year 366 days and the tropical year 365 days? In theory they are resp. 365.2564 and 365.2422 Days.
• Where is stone 20 of Cairn T standing (page 149), is not in plan of Cairn T (page 91)?
• Stone 8 of Knowth satellite 2 (page 162), looks comparable to orthostat 8 Knowth Site 14 (from Eogan [1986], plate 54)?

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