80 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [NoV. 19, 



fication in form would be quite natural on the supposition that the 

 freshwater beds of Auvergne were referable to the Miocene epoch. 

 The Melanopsis associated with the Melania in the hill of Gergovia 

 is more allied to the M. Dufourii than to M. buccinoides ; the Unio 

 seems peculiar at present to the locality. In regard to the age of 

 the Auvergne beds generally, I have not yet seen sufficient reason, 

 whether from the nature of the mammalian, reptilian, conchological 

 or vegetable remains imbedded in them, to abandon the idea of their 

 being Eocene, although it is true that they exhibit some characters 

 in common with the Miocene period. 



2. Geological Position of the Bitumen used in Asphalte Pave- 

 ments. By S. P. Pratt, Esq., F.R.S., F.G.S. &c. 



The bitumen which has been so extensively used for pavements, &c. 

 is found in considerable abundance, and of the best description, at 

 Bastenne, a small village in the south of France, about fifteen miles 

 north of Orthez. The geological circumstances connected with its 

 appearance being somewhat interesting, a short account of them 

 may be desirable. 



The country about Bastenne is formed of numerous small conical 

 hills two or three hundred feet high, separated from each other by- 

 deep narrow valleys or ravines; they are chiefly composed of a 

 coarse sandy limestone, which M. de Fresnoy places in the creta- 

 ceous system ; their upper part consists of variously coloured sands 

 and clays from fifty to sixty feet in thickness, the whole being co- 

 vered by gravel and sand, which extends for many miles in every 

 direction. The sands and clays are usually horizontal, but are oc- 

 casionally much disturbed and highly inclined ; whenever this oc- 

 curs it is evidently owing to the protrusion of igneous matter, which 

 is then found in connexion with them. The bitumen is worked in 

 three localities near to each other, and the following section was 

 made at the principal mine : — 



Gravel, 



12 feet of yellow sand, consisting of numerous thin layers, varying 

 in colour — red, yellow and white. 



2 feet of red and green clay. 



24 feet of coloured sands as before. 



1 foot of clay. 



6 feet of sands as before. 



4 feet of blackish sand containing a small quantity of bitumen. 



5 to 15 feet of bitumen which varies much in character, the upper 

 part consisting of looser and coarser sand, with a less proportion of 

 the bitumen, while the lower part is more compact, containing finer 

 sand, and being chiefly composed of bitumen. 



10 or 15 feet of sand without bitumen occurs in some places, 

 although where the bituminous sand is found of the greatest thick- 

 ness, it then rests upon the sandy limestone, which forms the chief 

 part of the surrounding country. 



