S M. Beaunieu on the 



measures from the primitive rocks on which they rest, if they 

 were both always exposed. The suite of elevations, consisting 

 of primitive rocks, rising above the coal district, might 

 be described by the same terms. 



Towards the south these heights belong to the principal 

 chain of the Pilat, separating the department of the Loire 

 from that of the Ardeche, the ramifications of which towards 

 the SW. form the limit of the department of the Haute- 

 Loire. On the west, the elevated primitive country rises 

 above the right bank of the Loire, for a short distance, 

 commencing from St. Paul de Corniilon, and afterwards 

 forms in the direction of the Rhone, a nearly continuous 

 ridge on the north of the coal basin, in the same manner as 

 the Pilat chain rises above it on the south and south west. 



The principal pait of these primitive rocks is composed of 

 granite, the most abundant ingredients of which are felspar 

 and mica. The first of these substances most frequently 

 presents itself in the form of a nucleus entangling plates of 

 mica, and occasionally talc. It is not rare however to find 

 the different ingredients of the granite more distinct ; the 

 mica is less abundant, and the crystals of felspar (frequently 

 of a roseate tint) become of considerable size. In nume- 

 rous places mica is the most abundant ingredient, the rock 

 then becomes a gneiss, and may be considered sometimes 

 as a griinit veine, and sometimes as a mica or talcose slate. 



On the west and north west the coal measures rest in 

 general immediately on granite ; on the south and south 

 west, ordinarily on gneiss, mica, or talcose slates, or even 

 Upon serpentine ; these rocks separate them from granite, 

 which is found on approaching the primitive ridges. This 

 primitive country contains metalliferous veins.* 



That we may not pass the limits we have prescribed 

 ourselves, we will now proceed to consider the country 

 formed of the coal-measures. 



* Mines of sulphuret of lead at St. Julian, Molin, Molette, and the 

 SiE. of Pilat; several veins of the same substance on the NW. of Rive 

 de Gier, towards Fontain, and St. Martin-la-Plaine. 



