1845.] PRATT ON ASPHALTE. 81 



This section was taken on the side of the hill where the bitumen 

 crops out, the upper beds being cut through to expose the bed; 

 its extent is about 2000 feet by 900; it terminates suddenly in one 

 direction, as the horizontal strata are cut off by a fault, by which 

 the beds are elevated to an angle of 70° or 80°. 



In the sands and clays no fossil remains have been met with except 

 occasionally small pieces of lignite, and the bitumen is generally free 

 from any extraneous matters, except in two localities, where numerous 

 marine shells are found, which may be referred to the miocene period. 

 In one of these, where the bed of bitumen is from ten to twelve feet 

 thick, the shells are disposed in numerous layers at a few inches' 

 distance from each other, — the shells of the same kind generally form- 

 ing distinct layers, although occasionally, where the layer is thicker, 

 many species occur together ; where the mass has been cut through 

 vertically, the appearance is very striking, bright white lines ap- 

 pearing on the black bed of bitumen. The shells are not broken or 

 disturbed, nor are the valves separated from each other ; they are, 

 on the contrary, perfectly preserved, the most minute markings ap- 

 pearing upon them when freshly dug up, but (in consequence of 

 the loss of the animal matter) they fall into powder upon being 

 exposed to the air. Notwithstanding this, perfect casts may be 

 readily procured, as they easily separate from the sandy mass. The 

 bitumen has evidently been forced into them in a soft or liquid 

 state, as the smallest cavities are filled, and this must have taken 

 place after their deposition in the sands in which the animals lived. 

 The date of this formation (as indicated by the numerous species 

 which have been determined) may be referred to the miocene sera; 

 and as the eruption of bitumen is evidently connected with the 

 appearance of the ophite^ an igneous rock, which has produced 

 such great changes in the Pyrenees, a limit may thus be obtained 

 for these changes. The bitumen worked in the other localities ap- 

 pears under similar circumstances, except that no shells have been 

 found in it ; the bed is nearly horizontal, dipping slightly towards 

 the centre, where it becomes of greater thickness ; indeed it is said 

 the depth has not been reached in one part where it is generally sup- 

 posed to have risen from beneath. The bitumen is easily cut when 

 first exposed, but in a few days it hardens so much as to become 

 incapable of purification ; the purification is effected by boiling the 

 sandy mixture in a large quantity of water two or three times, when 

 by continued and careful stirring the sand gradually settles to the 

 bottom, while the pure bitumen rises to the surface and is taken off. 



3. On the Occurrence of Coal in Formosa. By — Cooper, Esq. 



Specimens of this coal were exhibited to the meeting, but it did 

 not appear from the notice under what geological conditions the 

 coal existed. 



VOL. 11.— -PART I. 



