EXCURSION TO THE PYRENEES 35 



with two masses of ophite, is exposed by the side of the railway 

 line, cutting a series of limestones interstratified with marls, 

 which is supposed to be of Triassic age. But little can be seen 

 of the mutual relations of the several rocks or of their contacts. 

 Lacroix states that the nepheline syenite and the ophite appear 

 as little masses penetrating the Triassic limestones. He thinks 

 the nepheline syenite is later in age than the ophite, which 

 seems to surround it, but there appears to be no evidence from 

 their field relations which makes it improbable that they are 

 differentiation products of the same magma. The occurrence of 

 the nepheline syenite, from which all the Pouzac material in 

 collections the world over is derived, is barely sufficient in 

 size to furnish a working face for a single small quarry. (See 

 Fig. 3.) The rock is much decomposed, the sandy disintegra- 

 tion product being used for repairing the roads in the vicinity, 

 but fresh material may be obtained from the numerous bowlders 

 of decomposition. Small bostonite dikes occur in the limestone 

 near the contact. The marly beds are filled with dipyre and the 

 limestones contain little albite crystals, both minerals being 

 attributed to the metamorphosing action of the ophite. The 

 ophite itself is in many places filled with dipyre, which is, how- 

 ever, believed by Lacroix in this case to be the result of 

 weathering. 



On leaving Bagnieres-de-Bigorre the party drove up the 

 valley of Campan to Payole, a remote hamlet in the mountains, 

 near which a quarry has been opened in a marble of Devonian 

 or Carboniferous age, the stone being sent to Bigorre to be 

 sawn and polished. The rock, which is known as Marbre de 

 Campan, has a reddish or a grayish color and a linear brecciated 

 structure, which produces a handsome effect on the polished 

 surface, and which appears to be caused by certain laminae in 

 in the rock, rich in carbonate of lime, breaking apart under the 

 pressure to which the rock has been subjected, while the inter- 

 vening laminae, rich in argillaceous matter and more plastic, 

 have been forced in between the calcareous fragments and now 

 cement these together. 



