263 ANNALS NEW YORK ACADEMY OF SCIENCES 



In descending the Enne valley from Cransac to Viviez, one finds only 

 few and isolated exposures along both the railroad and the wagon road. 

 For the most part the sandstones, as shown, are not very coarse. The 

 coal of the Bourran system is cut by the stream, but the thin beds, being 

 without economic importance at present, are not mined, and no trace of 

 them was observed along the roads. At a very little distance from Aubin, 

 one passes abruptly from Coal Measures to gneiss and to granite as by 

 a fault. This granite must be largely of the type which yields readily to 

 weathering, as the topography is almost as rounded as that in the basin. 



From Viviez to Decazeville along Eiou Mort, the conditions are. unlike 

 those observed in the Enne valley. At Viviez, one is in the mica schists, 

 which are less yielding than the granite west from Aubin. The Eiou Mort 

 valley passes abruptly from the bold angular hills of schist to the rounded 

 hills of the Coal Measures. But before reaching the latter, one crosses 

 a narrow prong of microgranulite, which intervenes between the schist 

 and the Coal Measures. The contact with the latter rocks is not shown 

 at road level on either side of the valley, but on the northerly side the 

 concealed space is very small, and one comes quickly to a great conglom- 

 erate with the pebbles all rounded and frequently six inches in diameter. 

 The exposures begin opposite the pottery at Laboudie and continue to 

 within half a mile of Decazeville, the higher beds being less coarse and 

 containing much shale as well as fine-grained sandstone. 



On the southern side, everything is concealed beyond the microgranu- 

 lite exposure for almost half a mile by a thick deposit of stream clay, used 

 in the pottery. Beyond that the conglomerate is shown, containing peb- 

 bles of white quartz, white mica schist, some of gneiss and very many of 

 microgranulite. These pebbles are smaller than those seen on the north- 

 ern side and are from one to three inches in diameter. The source of the 

 material is from the direction of Viviez, as suggested by Bergeron, Jardel 

 and Picandet. At about 200 yards farther, as one reaches the outskirts 

 of Decazeville, an imperfect exposure at the roadside shows higher rocks 

 for 100 feet, 



Feet 



1. Conglomerate with some shale 10 



The pebbles are one fourth of an inch to one inch; there 

 are very few of white quartz, white mica schist and gneiss 

 prevail ; none of microgranulite was seen. 



2. Shales, weathering light gray 15 



Contain pockets of coal 2 to 3 inches thick ; the shales are 

 contorted and the coal pockets may be fragments of a con- 

 tinuous bed. 



3. Shales and shaly sandstones 10 



The dip of No. 3 is eastward at about 25 degrees. 



