302 



PEOF. T. Gr. BOKNET 03* THE 



to the sections of the He de Groix, Quimperle, and Morlaix. The 

 physiography of all this part of Brittany singularly resembles that 

 of Cornwall and the adjacent districts of Devon. There are the same 

 wide and gently undulating plateaux and low rolling hills, the same 

 tracts of grey granite and of shivery slate, the same steep-sided valleys, 

 which at last are occupied by the sea, and sometimes become veritable 

 fjords studded with hummocky islands : there are the same bare far- 

 reaching moors covered with gorse and ling and heath : nay, even in 

 the minor features, due to the hand of man, the likeness continues, 

 in the dolmens and menhirs of olden times, in the cottages and the 

 dykes of earth and stone that replace hedges among the fields — even 

 in the irregular twists and turns of the lanes ! 



Brittany, where I saw it, is a rather difficult country for the 

 geologist. Except on the granite moors and on the sea-coast, and 

 occasionally in the valleys, natural sections are rather rare, and the 

 most favourable localities, as it happens, are often far away from 

 the only convenient halting-places. As the country is not densely 

 peopled, artificial sections are not very common. Hence one may 

 often walk a considerable distance without seeing any thing but 

 woodland or cultivated fields. The task, then, of the geological 

 surveyors must have been a laborious one, and I beg leave to 

 express my admiration of the manner in which it has been accom- 

 plished*. 



(1) The He de Oroioc. 



The admirable memoir by Dr. C. Barroist on this out-of-the-way 

 locality makes it needless for me to describe in detail its geology. 

 I will merely record the impressions which I formed during my 

 examination of the eastern half of its coast. This is generally 

 rocky, occasionally precipitous, but, as a rule, easily examined. The 

 dominant rock is a mica-schist ; that of the greatest mineralogical 

 interest is the ampJiibolite a glaucopliane described by Dr. Barrois. 

 Of the former there are several varieties. The commonest contains 

 chloritoid as a constituent ; garnets are frequently present. Besides 

 this there are some felspathic, staurolitic, and graphitic schists. 

 These schistes a chloritoide are generally full of a well-developed 

 silvery mica (paragonite ?), and the red garnets commonly vary from 

 the size of a pin's head to that of a small pea. The structure and 

 composition of the group has been so fully worked out by Dr. Barrois, 

 that I content myself with referring to his paper. I will merely add 



* The circular of invitation, issued by the Societe Geologique de France, 

 contains a very complete list of works dealing with the geology of Brittany. 

 As this is a long one, and as a copy is preserved in the library of the Geological 

 Society, I have thought it needless to add a bibliographical section to this 

 paper. As the questions mentioned above are in most cases comparatively 

 modern, I have not deemed it necessaiy to examine the older works, and to 

 some in the list I have not access, but I have freely consulted the various 

 papers by Dr. C. Barrois, Mr. Whitman Cross, and Dr. Le Hir, which deal with 

 the districts visited by myself, and I took with me the sheets "Lorient " and 

 " Chateaulin " of the French geological map. Those including the remainder 

 of Brittany are not, I believe, as yet published. 



t Ann. de la Soc. Geol. du JSFord, t. si. p. 18. 



