1848.] MURCHISON ON THE STRUCTURE OF THE ALPS. 255 



fectly seen in the tract between the Brenta and the Piave, are taken 

 up and clearly displayed in the Monferrato ridge, and that the Su- 

 perga exhibits, on the one hand, a downward transition from what has 

 been considered true and pure miocene into nummulitic strata, and 

 upwards, on the other, into the richest subapennine or pliocene 

 marls and sands. The great hiatus on the northern flank of the Alps 

 may represent, perhaps, the upper portion of eocene, and the lower 

 part of what has been termed the miocene age, whilst on the south, evi- 

 dences have been left, of apparent transitions from one to the other. 



The conclusion therefore is, that without quitting the Alps and 

 their immediate flanks, we may argue for or against the independence 

 of several formations, according to the tract we survey. In England 

 the coal is generally conformable to the mountain or carboniferous 

 limestone. But now we know, that what is true in England and the 

 west of Europe, is not so in certain parts of Bohemia and Poland. 

 In these two countries a great dislocation has taken place after the 

 deposition of the mountain or carboniferous limestone with its large 

 Producti, and before the accumulation of the overlying coal-fields ; 

 the former being highly inclined together with Devonian and other 

 palaeozoic rocks, whilst the latter are horizontal. 



Nothing, however, that I have stated must be taken as militating 

 against the indisputable pheenomena of dislocations having occurred in 

 one region whilst adjacent countries remained quiescent, — phaenomena 

 which often enable us to mark the seras of such disturbances. It is 

 not against such general views of M. E. de Beaumont that I contend, 

 but simply against the abuse of them, in the hands of those who would 

 magnify into too great importance local and partial lines of rupture. 

 At the same time, I cannot doubt that great mutations of outline have 

 taken place at different periods, not only in and along the same chain 

 of mountains on lines parallel to each other, but even at different 

 periods upon the very same line. Judging from the analogies in 

 existing nature, such events might well indeed be supposed to happen 

 upon any one line of fissure, where the earth's crust had been once 

 much weakened by rupture. On this point I may revert to proofs, cited 

 by myself in the north-eastern portion of the Silurian region of the 

 British Isles, to show that similarly constituted igneous matter had 

 been successively extruded along the same line of fissure or vent of 

 habitual eruption, at one period mingling and alternating with the 

 Silurian sediments, afterwards throwing them on edge, next affecting 

 carboniferous strata which had been deposited on the edges of the 

 Silurian rocks, and at a subsequent epoch cutting in dykes through 

 the horizontal new red sandstone, thereby isolating a basin of lias*. 

 Now, all this occurred upon one and the same line at those successive 

 epochs. 



In concluding this portion of the memoir, I must further be excused 

 when I refer to another chapter of the ' Silurian System f ' for what 

 I consider to be a true delineation of Alpine phsenomena, although on 

 a smaller scale. In the Alps, as in Siluria, we see local divergent 

 strikes, sometimes of considerable extent, amidst rocks of the same 



* Silurian System, pp. 294 et seq. f See Chapter XLII. p. 572. 



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