of European Rocks. 157 



in one of his late letters to me, states, that mounting the Val 

 Bedretto from Airola to the foot of the Col, which leads into 

 the Haut Vallais, he found "an alternation many times repeat- 

 ed of small beds of a compact and grey-black limestone, and a 

 nearly black limestone mixed with clay slate thickly studded 

 with crystals of garnets and staurotides. Both the one and 

 the other of these rocks contain a considerable number of be- 

 lemnites transformed into white calcareous spar, but of which 

 the general forms and alveoli are nevertheless very visible, and 

 can leave no doubt as to the nature of the fossils. As these 

 limestone beds are the prolongation of those in which the gyp- 

 sum of the Val Canaria is found, and as these are the same 

 with those in which the dolomite of Campo Longo occurs, we 

 can assure ourselves that all the curious mineralogical phaeno- 

 rnena of the St. Gothard have been introduced into beds con- 

 temporaneous either with the oolite series or the greensand." 

 Now, when such important changes as those noticed by my 

 friend M. Elie de Beaumont can be fairly traced, what may we 

 not expect to find in the sequel, when geologists shall cease to 

 be contented with referring a particular mineralogical struc- 

 ture to the old divisions transition and primitive, of which the 

 former seems only to have been created as a geological trap- 



Unstratified Rocks. — This great natural division is one of 

 considerable importance in the history of our globe. To the 

 rocks composing it, and the forces which threw them up, may 

 be attributed the dislocations and fractures in the stratified 

 rocks every where so common, and in many instances their ele- 

 vations into lofty mountain ranges. In many of the great 

 chains the trap rocks are visible along their line of elevation, 

 as was first observed by M. Von Buch in the Alps, — on the 

 southern side of which they are exposed at intervals ; and it is 

 on this side that there is so much dolomite in the limestones. 

 To assert that igneous rocks cannot be present along the whole 

 of this line because not every where visible on the surface, is 

 like affirming that there is no table beneath a cloth spread on 

 it, except in the cases where there may be a few holes. We 

 are too apt in judging of the mass and thickness of rocks to 

 compare them with our own size, and imagine them enormous, 

 expressing surprise at the immense forces which it must have 

 required to raise such masses into mountains ; when if they 

 were compared, as they ought to be, with the mass of the world, 

 the thickness becomes trifling, the highest mountains insignifi- 

 cant, and the forces required to raise them comparatively 

 .small. 



That granitic, trappean, and serpentinous rocks have exer- 

 cised a great influence on the present position of the stratified 

 rocks, few geologists will doubt. The igneous origin of the 

 two former is also very generally admitted ; but though the 



