and IVritings of Baron Leopold von Buck. 221 



in such a position that we cannot easily avoid regarding its 

 presence as the cause of these extraordinary peculiarities in 

 the form of the external surface. 



The striking alteration which the proximity of the black 

 porphyry causes in the nature of the rocks with which it comes 

 in contact, is just as important. Wherever it is connected 

 with the prevailing limestones, these assume a different cha- 

 racter. The limestone in most cases loses its distinct stratifi- 

 cation, and is converted into a formless mass, which is fissured 

 in irregular directions ; its usually compact, coarsely earthy 

 condition, has passed into a peculiar, crystalline, sharply granu- 

 lar structure, resembling that of sugar. A more minute ex- 

 amination shews even that this altered saccharine mass is no 

 longer a carbonate of lime, but a combination of carbonate of 

 lime and carbonate of magnesia, which was previously known 

 in other places, and had been distinguished by mineralogists 

 under the name of Dolomite. 



These are the most essential, and in part surprising new 

 facts, which Buch discovered in a district of the Alps which 

 had previously not been minutely investigated. The most of 

 them are described in a series of memoirs which are published 

 together in Leonhard's Taschenhuch for 1824, and which are 

 accompanied by an excellent geognostical map, and by very 

 remarkable sections. 



The consequences which he deduced from these observa- 

 tions are of the highest importance. He found that the por- 

 phyries discovered by him are to be observed again in several 

 places of the region of the Alps, to the east as well as to the 

 west of this principal district, and always in the direction of 

 the chief line of the Alps, at the foot of steep mountain 

 chains. On that account he no longer doubted that the 

 issuing forth of this newly-discovered porphyry-formation 

 had been the cause which elevated the gigantic chain of the 

 Alps, and placed it in its present position. Whenever these 

 porphyries appear, there we find along with them the singular 

 snow-white saccharine dolomite rocks. He thence drew the 

 conclusion that the porphyry had converted the limestone into 

 dolomite in a peculiar manner. The limestone was fissured 

 throughout, and, by means of the passages thus affbrded, the 



VOL. XXXI. NO. LXII.— OCTOBER 1841. P 



