30 FRANK DAWSON ADAMS 



The following day, August 5th, the regular work of the excur- 

 sion began, two visits being made, from Ax-les-thermes as head- 

 quarters, on consecutive days, to the contact of a large mass of 

 granite, several miles to the northeast of Ax-les-thermes in the 

 heart of the Pyrenees, with a series of shales and limestones 

 believed to be of pre-Cambrian age. The exact age of the 

 granite is not known but it is younger than the Carboniferous 

 and older than the Lias. 



The contacts seen on the first day, were chiefly in the vicinity 

 of the beautiful little L'Etang de l'Estagnet, from which there 

 rise on either side great walls of bare rock, and well graded talus 

 slopes affording abundant exposures. (See Figure I.) 1 The 

 normal granite of the district is light in color, poor in iron 

 magnesia constituents and contains large porphyritic feldspars. 

 It often shows marked evidences of dynamic action. The shales 

 near the contact are hardened, being converted into a hornstone,. 

 said by Lacroix to be in many places " feldspathise," but the 

 most interesting feature of the excursion was the contact of the 

 granite with the limestone. This limestone, which is gray in 

 color and highly crystalline, contains many little bands of 

 silicates, representing impure laminae in the original rock, which, 

 especially on the weathered surface, emphasize its stratified 

 character in a most striking manner and often display the most 

 complicated contortions. The limestone in its whole character 

 and appearance exactly reproduces many occurrences seen in the 

 more altered limestones of the Hastings Series in the Archean 

 of Canada. 



Between the limestone and the granite, however, there is a 

 zone of rock, often very narrow but in some places, according 

 to Lacroix, as much as 800 meters wide, more basic than the 

 granite and termed by Lacroix, " Diorite " or " Roche Dioritique." 

 This completely surrounds certain isolated occurrences of lime- 

 stone and is believed by Lacroix to have been produced by the 



1 For the photographs which illustrate this paper, with the exception of that 

 reproduced in Fig. 2, the author is indebted to Professor Heinrich Ries, of Cornell 

 University. 



