Scrope's Memoir on the Geology of Central France. 36T 



itself in two lateral valleys, having their origin in the part of the plateau 

 occupied by the lava current, which, separating consequently into two 

 limbs, rushed down the declivities presented on either side. 



" The right hand branch first deluged and completely filled an area sur- 

 rounded by granitic eminences, and probably the basin of a small lake ; 

 thence entered the valley of Villar, a steep and sinuousgorge, which itthread- 

 cd exactly in the manner of a watery torrent, turning all the projecting 

 rocks, dashing in cascades through the narrowest parts, and widening its 

 current where the space permitted, till, on reaching the embouchure of the 

 valley in the great plain of the Limagne, it stopped at a spot called Font- 

 more, where its termination constitutes a rock about fifty feet high, now 

 quarried for building-stone. From the base of this rock gushes a plenti- 

 ful spring, the waters of which still find their way from Villar, beneath 

 the lava which usurped their ancient channel. 



" The branch v^hich separated to the left plunged down a steep bank into 

 the valley of Gresinier, replacing the rivulet that flowed there with a black 

 and shagged current of lava, entered the limits of the Limagne at the 

 village of Durtol, and continuing the course marked out by the streamlet, 

 turned to the north, occupied the bottom of the valley lying between the 

 calcareous mountain Les Cotes and the curtain of granitic rocks, and final- 

 ly stopped on the site of the village of Nohanent, Here, as at Fontmore, 

 an abundance of the purest water springs from below the extremity of the 

 lava current. The various rills which drain the valley of Durtol and its 

 embranchments have recovered their pristine channel, and filtering through 

 the scoriform masses which always form the lowest surface of a bed of 

 lava, flow on unseen till the rock above terminates, and they issue in a 

 full and brilliant spring. Above this point, consequently, is seen the 

 anomaly of a valley without any visible stream ; and the inhabitants of 

 Durtol are condemned, in seasons of drought, to the strange necessity of 

 seeking at Nohanent, a distance of two miles, the water which flows there 

 beneath their own houses. 



" In its appearance, the Cheir of Pariou is even more bristling and rugged 

 than those already described. M. D'Aubuisson justly compares it to a 

 river suddenly frozen over by the stoppage and union of immense frag- 

 ments of drift-ice." 



This interesting description is followed by an account of the Puys de 

 Sarconi, a group of volcanic hills, whose structure throw much light on 

 the mode and formation of the dome-shaped masses of trachyte which oc- 

 cur in so many volcanic districts. Our limits, however, will not allow us 

 to transfer it to our pages. 



Iir the departments of the Upper Loire and of Ardeche, there occiir a 

 very extensive system of volcanic rocks, of which Mont Mezen is the 

 most elevated. These rocks seem to have proceeded from the S.E. side of 

 Mont Mezen, from which two principal embranchments of clinkstone 

 (phonilite) have been projected, one to the S. and the other to the N.N.W. 

 The first exhibits itself in between twenty and thirty neighbouring rocky 

 eminences of considerable magnitude ; biit the second, which is of amoist 



