302 O. A. Lebour — On the Submergence of Is. 



■upon the land ; one of the churchyards being already half eaten 

 away by the waves of high tides, and displaying a by no means 

 pleasing collection of bones below high-water mark. Moreover, it is 

 asserted by sailors that the weird rock to the west of the ruins, 

 well known as the Torche de Penmarch, is decreasing in height, and 

 is no longer as excellent a land-mark as it was in former years. 

 Proceeding westward from this point, we soon come to the Anse de 

 Benodet, where, on the shores of the He Tudy, I was fortunate 

 enough to discover two lines of boundary mounds, or stone dykes, 

 which were continued some distance below low-water mark, thus 

 plainly proving a subsidence of this low-lying shore at no very 

 distant date. It is, however, further west still that the best and 

 clearest proofs of depression are to be found, in the Bay de la Foret, 

 the very name of which should cause geological ears to prick up. 

 This bay is small, the shores consisting of low-rounded rocks of 

 very coarse-grained granite. It is two-thirds of a circle in shape, 

 and is much used for oyster culture. It is shallow, the bottom 

 being everywhere a mass of coralline. In dredging, however, for 

 annelids, etc., I often brought up nuts and bits of wood, black and 

 soft, as they are found in peat-bogs. During very low tides the 

 shelving beach is seen to be studded very thickly with similarly 

 blackened and decomposed trunks of trees (mostly oak and birch) 

 apparently embedded in a layer of peaty mud full of nuts and leaves. 

 In order to see these trunks, much clearing of the overlying sand 

 is generally required, but their presence is so well known to the 

 fishermen of the coasts, that it is always given by them as the 

 origin of the name of the bay. That we have here a sunken forest 

 there can be no doubt, and that the date of its submergence is by no 

 means ancient (geologically speaking), is proved by the fact that on 

 the western side of the bay the old wood is continuous with a 

 living one on land at a place called Kerafloch. Besides this direct 

 proof of submergence, I have it on the authority of a French naval 

 officer, very familiar with the Brittany coast, that the lies de Grlenan 

 (some eight miles to the south of the Bay de la Foret) are in the 

 modem charts sensibly smaller than they are drawn in the older 

 maps. This is to some degree corroborated by the Ormer (Haliotis) 

 fishers, who assured me that at the present day the Ormers are found 

 much nearer the lighthouse on Penfret Island (one of the Gldnan 

 group) than they were formerly.^ These two statements ai'gue a 

 rather rapid encroachment of the sea upon the land, and one which, 

 when viewed in connexion with the other data furnished by the 

 coast of the main-land, must in all probability have been continuing 

 for a very considerable time. With such facts before us then, it is 

 only necessary for our purpose to inquire whether the amount of 

 depression displayed by them is sufficient to account for the sub- 

 mergence, fifteen centuries ago, of a portion of the present Bay of 

 Douarnenez. In order to arrive at any results in this matter, the 

 depth of the Bay of Douarnenez must of course be taken into ac- 

 ^ The Ormer can only be collected during very low tides, as its habitat is con- 

 siderably below ordinary low-water mark. 



