300 G. A. Lehour — On the Submergence of Is. 



in. — The Submergence of Is, in Western Brittany. 



By G. A. Lebour, F.G.S., F.R.G.S., 

 of the Geological Survey of EEgland. 



IT has frequently been found that in cases of depression or eleva- 

 tion of land the records of historians have corroborated the in- 

 ferences of geologists. The works of the ancient geographers have 

 also been of use in this way. It is, however, more rarely that a 

 tradition receives confirmation at the hands of geological observers, 

 and this it is which leads me to call the attention of the readers of 

 the Geological Magazine to the subject of the present paper. 



The tradition to which I wish to refer is one which has for many 

 centuries been current in Lower Brittany, and the substance of it is 

 this : that in the time of King Gradlon, that is, in the fourth or fifth 

 century, the chief town of his kingdom was situated far to the West 

 of the present land where is now the Bay of Douarnenez ; that the 

 land on which it stood was very low, and in constant danger from 

 inroads of the sea, which was kept out by what the ballads on the 

 subject call " gates," but which may have been some kind of dykes. 

 The name of this town was Is, and it was the seat of the king's 

 government. The legend then tells how, by a romantic series of 

 events, the town and the surrounding low-lying land were sub- 

 merged, the king only saving himself at the expense of his daughter 

 Dahu, whom he flung into the sea from the pillion on which she was 

 escaping with him. 



Now there are a number of circumstances which tend to give this 

 legend more weight than such tales usually deserve. Most of these 

 arguments in favour of the existence of Is are stated at length in the 

 Chronicles of the Ligue in Brittany, by Chanoine Moreau, who wrote 

 about, the beginning of the seventeenth century. The principal 

 among them are as valuable now as they were in the time of Moreau, 

 and the utter absence of variation in the tradition as it was known to 

 the Bretons then and as it is told and sung by them now, is some 

 evidence to its original truth. The facts which are explicable only 

 on the assumption of the existence of the town and land in question 

 are chiefly these : — 1. That several well-made roads, which are even 

 now very easily traced across the country, run from various inland 

 points (for the most part ancient shrines) in Brittany to the shores 

 of the bay, and that these roads, which have at present no conceiv- 

 able object, would, if prolonged, converge at a point within the bay, 

 some miles from land. 2. That the Abbots of Landevenec (a large 

 and rich abbey, founded by King Gradlon) were bound by the terms 

 of their tenure to come and take formal possession at a rock on the 

 beach at Pentrez, which is the point nearest to the supposed site of 

 the lost town. This ceremony was continued until shortly before 

 the great Revolution, and it was always understood that the Pentrez 

 rock was used as a substitute for Is, which could no longer be reached. 

 3. That many of the villages and towns in the vicinity of the bay 

 have the termination is, which is a point in the evidence to which I 



