Correspondence — Mr. A. Harker. 285 



intrusion of granophyre, on the other hand to the gahbro-magma 

 having enclosed considerable masses of the basic lavas of the 

 district, which are themselves highly metamorphosed. 



2. " The Geology of Monte Chaberton." By. A. M, Davies, Esq., 

 B.Sc, F.G.S., and J. W. Gregory, D.Sc, F.G.S. 



The importance of the Chaberton district, as affording a key to 

 the general geology of the Cottians, is explained, and the opinions 

 of previous observers referred to. The mountain vv^as examined 

 from three sides — that of the Grand Vallon ; the approach from 

 Mont Genevre by the Col de Chaberton ; and that of the Clos des 

 Morts Valley. The following are the conclusions arrived at : — 



(1) The well-known Chaberton serpentine is intrusive into the 

 calc-schists, and yields fragments to the cargneules of the Trias ; it 

 is, therefore, a pre-Triassic intrusion. 



(2) There are on the mountain other fairly basic schistose rocks 

 (quartz-chlorite-schists) which cut the Trias, and are therefore post- 

 Triassic. 



(3) The contorted beds in the Clos des Morts Valley are 

 fossiliferous limestone, and it is from them that the fallen blocks 

 pi'eviously recorded were derived. The only recognisable fossil 

 is Calamophyllia fenestrata, Reuss, a characteristic coral of the 

 Gosau beds. In spite, therefore, of the doubts of Kilian and 

 Dienei', the opinion expressed by Neumayr as to the existence of 

 Cretaceous rock in this part of the Alps is confirmed. 



(4) The earth-movements of the mountain are described ; they 

 include ordinary folds, inversions, faults, and an important thrust- 

 plane. 



(5) It is suggested that in addition to the two series of intrusive 

 rocks above-mentioned as pre- and post-Triassic, a third series of 

 late Cretaceous or Tertiary date may be represented in the Mont 

 Genevre and Eocciavre masses. 



3. " Cone in Cone. How it occurs in the Devonian (?) Series 

 in Pennsylvania, U.S.A., with further details of its [Structure, 

 Varieties, etc." By W. S. Gresley, Esq., F.G.S. 



The author describes cone-in-cone structure occurring in the 

 Portage Shales of Pennsylvania, and gives details concerning the 

 nature of the structure as seen in these shales. He criticizes 

 the explanation of Mr. J. Young as to the origin of the structure, 

 and concurs in a great measure with the views of those who have 

 suggested that the formation was due to pressure acting on con- 

 cretions. 



ooiaiaESiPoiDTnDiBisrozE]. 



A PHYSICAL CONTEIBUTION TO DYNAMIC METAMOEPHISM. 



Sir, — Among recent physical researches, one of the most interest- 

 ing to geologists is embodied in two papers by Prof. M. Carey Lea 

 on " Endothermic Reactions effected by Mechanical Force." ^ The 

 author shows by direct experiment " that mechanical force can bi'ing 

 about reactions which require expenditure of energy, which energy 

 1 Amer. Journ. Sci. 1893 (3), vol. xlvi. pp. 241-244, 413-420. 



