Geometry in Irish Maps

Geometry in Irish Maps

Ptolemy's Ibernia Britannica. (c. 87 - 150 AD). It is tempting to see in the three islands centered on the line of longitude in the Irish Sea (Mona, Limnos and ?) the source for the three mysterious islands which sometimes appear in the first printed maps of  Ireland

Hiberniae Britannicae Insvlae Nova Descriptio published by Abraham Ortelius in 1592. Note the phantom islands below Dublin on the east coast.

The underlying structure of the map is a fusion of circle and square, and the 'islands' can be seen to function as the eastern side of that square. The rendering of the North half of Ireland as a circle is very reminiscent of the depiction of South Wales in Cambriae Typus which is also based on a circle - the circle which is delineated by Gwydion's pig sties in Math vab Mathonwy. These two maps (Cambriae Typus and Hiberniae Britannicae), are clearly part of the same tradition of Cartography which generated the 'Angel of Lincoln', The Lion of Scotland and The Unicorn of England.

Mercator's Irlandia of 1602 has relegated the phantom isles to mere sand banks as 'South ground', 'Middel ground' and 'North ground' but still retains the tradition of the Giant's Head with it's Lake of the Red Eye.

The following is Lady Guest's translation of the famous 'night watchman scene' from the Second Branch or Branwen Daughter of Llyr.

The King's Head.

Then he proceeded with what provisions he had on his own back, and approached the shore of Ireland.

Now the swineherds of Matholwch were upon the sea-shore, and they came to Matholwch. 

"Lord," said they, "greeting be unto thee." 

"Heaven protect you," said he, "have you any news?" 

"Lord," said they, "we have marvellous news, a wood have we seen upon the sea, in a place where we never yet saw a single tree." 

"This is indeed a marvel," said he; "saw you aught else?" 

"We saw, lord," said they, "a vast mountain beside the wood, which moved, and there was a lofty ridge on the top of the mountain, and a lake on each side of the ridge. And the wood, and the mountain, and all these things moved." 

"Verily," said he, "there is none who can know aught concerning this, unless it be Branwen."

Messengers then went unto Branwen. "Lady," said they, what thinkest thou that this is?" 

"The men of the Island of the Mighty, who have come hither on hearing of my ill treatment and my woes." 

"What is the forest that is seen upon the sea?" asked they. 

"The yards and the masts of ships," she answered. 

"Alas," said they, "what is the mountain that is seen by the side of the ships?" 
"Bendigeid Vran, my brother," she replied, "coming to shoal water; there is no ship that can contain him in it." 

"What is the lofty ridge with the lake on each side thereof?" 

"On looking towards this island he is wroth, and his two eyes, one on each side of his nose, are the two lakes beside the ridge."

Mercator's map, as well as maps derived from it, also kept to a strict underlying geometry, which in this case is comprised of two adjacent squares.

Giraldus Cambrensis' (Gerald of Wales, c. 1146-1223) map of Ireland from the Topographia Hiberniae, suggests that he was not really capable of producing the now lost Totius Kambria Mappa, which is sometimes attributed to him and which Henry Owen described as 'a map of the whole of Wales, with the mountains. rivers, towns, castles and monasteries carefully set out'. 

(See 'The Journey of the Swine' for the significance of this).


On the other hand it is clear that Rhygyfarch ap Sulien,, judging 

from the following excerpt from his Vita Davidus, possessed a 

more sophisticated concept of a map of Ireland:  

"Rejoice, Patrick, for the Lord hath sent me to you that I may show you the whole of the island of Ireland from the seat which is in Vallis Rosina," which now is named "the Seat of Patrick." And the angel says to him, "Exult, Patrick, for you shall be the apostle of the whole of that island which you see, and you shall suffer many things in it for the name of the Lord your God, but the Lord will be with you in all things which you shall do, for as yet it has not received the word of life; and there you ought to do good; there the Lord has prepared a seat for you; there you shall shine in signs and miracles, and you shall subdue the whole people to God. Let this be to you for a sign. I will show you the whole island. Let the mountains be bent; the sea shall be made smooth; the eye bearing forth across all things, looking out from [this] place, shall behold the promise." At these words he raised his eyes from the place in which he was standing, which now is called "the Seat of Patrick," and beheld the whole island.