12 Rev. W. D. Conybeare on a Geological Map of [Jan, 



they trend inland, and are succeeded by secondary hills. The 

 Alps, which may be said to expire on the side of Italy, appear 

 rather to be continued as to their geological constitution in the 

 primitive chains of Corsica and Sardinia, situated directly oppo- 

 site the termination of the Maritime Alps against the coast, and 

 in the line of their prolongation. 



From the Gulf of Genoa, the Alps pursue their course first to 

 the NNW, through Piedmont and Savoy ; then turning suddenly 

 to the E through Swisserland, the Tyrol, and Stiria. The primitive 

 and transition chains have together an average breadth of 

 between 50 and 60 miles. These are succeeded by exterior 

 zones of limestone, principally coeval with the magnesian lime- 

 stone and oolitic series, the carboniferous series being apparently 

 absent,* or at most of very limited occurrence. The beds of the 

 Alpine rocks where these are stratified are generally vertical ; 

 the bordering chains exhibit marks of the greatest disturbance, 

 their strata being contorted and dislocated. Thus on the north 

 all the recent calcareous chains appear to dip towards, instead 

 of rising against, the central and primitive ridges. The three 

 following sections taken from Ebel will give a general idea of 

 the distribution of the older rocks in the Swiss portion of the 

 Alps : 



1. Over the Bonhommc and Mount Cenis. 



Clayslate (Sallenche). 



Micaslate and gneiss. 



Primitive limestone and clayslate. 



Gneiss, granite, micaslate, hornblende slate 



(the Bonhomme). 

 Primitive limestone. 

 Gneiss and micaslate. 

 Primitive limestone and gypsum. 

 Unexplored interval along the upper valley of 



the Isere. 

 Primitive limestone and gypsum. 

 Primitive limestone and micaslate (Mount 



Cenis). 

 Gneiss. 

 Clayslate. 

 Serpentine. 

 Granite. 

 Serpentine. 



2. Over Great St. Bernhard. 



Compact felspar and slaty sienite. 



Greywacke slate. 



Compact felspar and slaty sienite. 



* Mr. de la Beche has, however, noticed traces of the coal formation in the Col. de 

 Baume. 



