368 Analysis of Scientific Books and Memoirs. 



remarkable cliaracter, constitutes a mountainous chain of numerous simi- 

 lar rocks covering a wide extent of country. 



" The uniformly progressive declination," says Mr Scrope, " of this 

 system of phonilitic summits from the Mezen to the bed of the river, 

 where they terminate, the two last leaning against the foot of the primi- 

 tive range of La Chaise Dieu on the opposite bank, proves them, in my opt- 

 nioiiy to he the remains of a single enormous kiva current, prior in date ta 

 the excavation o/"j;A<? rtc^wa/ channel of the Loire, and far the most con- 

 siderable in bulk and extent of any I have had occasion to observe in the" 

 Phlegraen fields of France. The space it appears to have covered is more 

 than tweniifsix miles in length, with an average breadth of six, containing, 

 therefore, a superficies of 156 square miles. Its thickness must originally 

 have been prodigious, and may be judged of by the mountainous portions 

 still remaining. Many of these rise to a height of 400 and 500 feet from 

 their base; and none, I believe, show any marks of a division into separate 

 beds, so that the whole colossal range must be supposed of a piece, the re- 

 sult of an individual eruption. It rests generally on granite, either im- 

 mediately, or with the intervention of basalt, but appears also to have 

 crossed a large angle of the calcareous fresh water formation which occurs 

 in the neighbourhood of Le Puy." 



Mr Scrope concludes the descriptive part of his work with an acccout 

 of a chain of volcanos in the Velay and Vivarais, which he considers as the 

 products of a later effect of volcanic activity. They cover uninterrupted- 

 ly a broad zone of the primitive plateau from Paulhaguet and Alegre to 

 Pradelle and Aubenas, and seem to be a prolongation of the chain of Puys 

 of the Auvergne. Numerous cones still mark the point at which these 

 eruptions took place ; and they are so thickly sown along the axis of the 

 granitic range that separates the Loire and Allicr from Paulhaguet to Pra» 

 delle, that they generally touch each other at their bases and form an al- 

 most continuous chain. Between Pradelle and Aubenas they are of less 

 frequent occurrence, and there are more to the south of the latter. A large 

 and productive group, however, exists to the N. E. of Pradelle in the 

 neighbourhood of Prezailles. Mr Scrope counted more than one hundred 

 andffty of these cones in the above tract. These cones are not so fresh 

 and well-preserved as those of Auvergne. Not many have an entire or 

 even a distinctly marked crater, and as the volcanic energy seems to have 

 been exerted far more furiously, the lava currents have been united into 

 one continuous and enormous current, where all are mingled and confounded. 

 Mr Scrope is of opinion that the most recent eruption of the district was 

 that whfch produced the double hill of Mont, S. E. of the Le Puy, and 

 which formed a small platform of columnar basalt called Montredon, rising 

 in the middle of the valley of the Borne, and resting on a shingle of pri- 

 mitive and volcanic boulders. 



Some of the most remarkable and interesting of the recent volcanic re- 

 mains in Old France, are those which occur on the deep declivity by which 

 the preceding escarpement is connected with the southern valley of the 

 Bas Vivarais and Languedoc. As seen from below, that front of the great 



