O:?^ THE VARIOLITIC ROCKS OE MONT GENEVRE. 



311 



small part of the floor of the upper and western portion of the 

 Chenaillet valley ; while the summits immediately above, and the 

 whole upland about the lakelets, as well as all the main walls of 

 this " vallon affluent de la Doire," consist of rocks entirely different 

 in their mode of weathering, colour, and degree of crystallization. 



Pinding serpentine on the eastern flank, Lory *, in his published 

 section, filled in the intervening space as " euphotides,'' and thus 

 unconsciously diverted the attention of observers from one of the 

 richest areas where variolite may be obtained in sit a. We must 

 recognize, however, that the igneous masses extend some way 

 towards the Cerveyrette, and euphotide may be there more pro- 

 minent. We hope at some future time to examine this southern 

 area ; but from the contour we judge that Lory's section traverses 

 the high ground near Le Chenaillet, to which his descriptions, as 

 above quoted, undoubtedly apply. 



Fig. 4. — Variolite-diabase. Spheroidal Masses with Variolitic 

 Selvages. North end of Le Chenaillet Ridge, above the Durance, 



The prevalent rock of the whole district at present under dis- 

 cussion is a compact grey-green diabase. The dykes already 

 described doubtless represent the coarser types of these widely 

 spread masses. The most striking character of the compactor series 

 is a tendency to spheroidal jointing. Sometimes, as among the 



^ " Carte et coupes geol. clu Brianronnais," Bull. Soc. gcol. France 2* ser 

 t. XX. (1863) p. 233. 



Q. J. G. S. No. 182. T 



