1823.] the principal Mountain Chains of Europe. 9 



topped by the schistose, and still more by the calcareous band 

 on the side of Spain ; the latter forming the Tours de Marbore, 

 Mont Perdu, and all the loftiest summits of these mountains. 

 What renders this circumstance more remarkable is, that this 

 limestone appears from its organic remains, (Echini and Alcyo- 

 nia), to be of comparatively recent formation. The specimens I 

 have seen approach nearly to those varieties of the younger 

 alpine limestone now generally considered as coeval with the 

 green sand formation of England. I have been favoured with 

 the sight of a very interesting letter from Dr. Boue, who has 

 recently examined this chain ; he observes that it is entirely 

 transition (transition slate and limestones, and marie), through 

 which, in various places, granitic masses protrude, occasionally 

 surrounded by gneiss and mica slate ; these latter rocks appear- 

 ing as they recede from the granite to pass into clay slate. He 

 adds that the various phenomena which have been alleged in 

 proof of the igneous origin of granite (granitic veins, fragments 

 of slate imbedded in the granitic masses, the elevation, contor- 

 tion, and dislocation, of the slates, together with their altered 

 character near the point of contact, &c), are here displayed on 

 the most remarkable scale, and with a clearness of evidence 

 nearly amounting to demonstration. He is even of opinion that 

 the slates called primitive may, in this instance at least, have 

 been only transition slates altered by the igneous influence ; the 

 transition limestone, in like manner, becomes converted into 

 granular limestone in approaching the granite. Great dykes of 

 greenstone and syenite also traverse the slate ; when these are 

 large, the limestones are in the same manner altered by their 

 contact, and may be seen at Pousac elevated and supported by 

 them. On the north of the Pyrennean chain old red sandstone 

 and traces of mountain limestone occur, succeeded by new red 

 sandstone with salt springs. 



(F.) Chains of the Middle Rhine, or the Vosges, the Black Forest, 

 the Bergstrasse, or Odenwald, and the Spessart. 



Were we to pursue the course of the great chains forming the 

 general boundary of the grand European basin, we ought, in the 

 next place, to proceed to the Alps ; but within the limits of this 

 basin there are several protruding primitive groupes, skirting in 

 places the course of the Rhine, and effecting a kind of subdivi- 

 sion between that part of the basin which lies in Northern 

 France, and that of Central Germany. The first of these pro- 

 truding groupes to be noticed are those which skirt the opposite 

 sides of the great Valley of the Rhine in its central region below 

 Basle ; namely, the Vosges, which rise on the left bank of the 

 river above Colmar and the Black Forest, or Schwartzwald on 

 the right bank. 



The Vosges exhibit granite, transition slate, limestone, and 

 porphyry. The greywacke near its contact with the porphyry 



