G. A. Lehour — On Western Brittany. 443 



dented, and forms an endless number of small bays, promontories, 

 and headlands ; as may be seen by glancing at the Eade de Brest in 

 any map. 



Along the southern granitic coast, the sea is very shallow for 

 some miles, and the numerous small islands with which it is studded 

 have exactly the same geological features as the mainland ; thus 

 showing that the southern granitic plateau has a much greater ex- 

 tension than the boundary of the coast alone would indicate. The 

 lies de Glenan are a case in point. 



3. General Surface Characteristics. — The two great watersheds of 

 the country are formed by the two central chains of hills, the space 

 between them or " swire," ^ which is very narrow and not much 

 below the average height of the two flanking ranges, being for the 

 most part covered with wet bog-land. 



The Montagues d'Arrhee supply the streams running to the north 

 and north-west, and the Montagues Noires those flowing to the south. 



Descending from these hills on either side, and proceeding to the 

 south or north, we find ourselves all the way to the sea in what 

 appears at first sight to be an exceedingly hilly and disturbed 

 country. The streams are innumerable, and flow at the bottom of 

 deep narrow rocky ravines, which intersect the country in every 

 direction. Their course is most tortuous, and continues, with scarcely 

 any noticeable difference of width or depth, alike through the hard 

 Silurian grits and their enclosed traps, the vertical or contorted leafy 

 metamorphic schists, and the variously-grained, easily decomposed 

 granites. What slight change there may be, however, is most dis- 

 cernible '^among the latter rocks, where the valleys are sometimes 

 somewhat wider and less winding than in the former. The jagged 

 appearance, moreover, of the rocky sides of these valleys tends to 

 increase the mountainous and rugged aspect of the scenery. This, 

 however, is only the result of a superficial view of tlie physical 

 features of this district, and is by no means in accordance with the 

 true facts of the case. These errors are perpetuated by the use 

 of sections across the country drawn on exceedingly exaggerated 

 vertical scales ; quite a universal practice abroad. 



By drawing horizontal sections on a true scale, cutting the whole 

 breadth of the peninsula, the height and distances being taken from 

 the large government maps of these parts, and by carefully going 

 over the ground along each line of section, added to a long acquaint- 

 ance with the country generally, I have been enabled to arrive at 

 the conclusions, the statement of which is the object of the present 

 paper. 



Following on j^aper one of these lines of section (a north and 

 south one) from the base of the Montagues Noires to the southern 

 sea-shore^ we are immediately struck by the absence of marked 



' I have ventured to iise the old north country word "swirc" to express the slack 

 between two hills. I think it might be a useful one to adopt in the description of 

 physical features. 



* The result would be exactly similar were we to follow the northern half of the 

 section from the hills to the north coast. 



