METAMORPHOSES OF ROCKS. 



79 



through the influence of granite, syenite, or 

 dioritic porphyry( =**«). 



Let me be allowed to refer particularly in 

 this place to the Parian and Carrara marbles, 

 which have become so necessary to the noblest 

 efforts of the sculptor, and which have served 

 but too long in our geological collections as 

 principal types of primitive limestone. The ef- 

 fects of the granite here reveal themselves 

 partly under immediate contact, as in the Pyr- 

 enees'**^), partly, as in the continent of Greece 

 and the islands of the ^gean Sea, through in- 

 terposed strata of gneiss and mica slate. In 

 both cases the process of transformation of the 

 calcareous rock is contemporaneous, but dis- 

 similar. It has been observed at Cubaea, in 

 Attica, and in the Peloponnesus, " that the rule 

 is, that the limestone which rests upon mica 

 slate is by so much the more beautiful and 

 crystalline as the schist is purer, that is, as it 

 is freer from argillaceous admixture." Mica 

 slate, as well as gneiss strata, present them- 

 selves at many deep points of Pares and Anti- 

 paros(=**^). If marine productions were discov- 

 ered [in ancient times] in the quarries of Syra- 

 cuse, and the " impression of a small fish" was 

 seen in the deepest of the rocks of Paros, as 

 we may infer from a notice in Origen, of the 

 old Eleatic philosopher, Xenophanes of Colo- 

 phon (=2*3), who conceived the whole of the 

 world to have been formerly covered by the 

 sea, we might believe in the remains of a floetz 

 stratum in this situation which had not under- 

 gone complete metamorphosis. The marble 

 of Carrara (Luna), which was employed before 

 the Augustan age, and was the principal source 

 of the material for statues so long as the quar- 

 ries of Paros remained closed, is a stratum of 

 the same cretaceous sandstone (macigno) al- 

 tered by Plutonic agency, which presents itself 

 in the insulated Alpine height, Apuana, lying 

 between gneiss -like micaceous and talcose 

 schistsC^"). Whether or not granular lime- 

 stone, formed in the interior of the earth, and 

 filling fissures in the manner of veins (Auer- 

 bach on the Bergstrasse), have ever been forced 

 to the surface by gneiss and syenite("i), I can- 

 not, through want of personal observation, take 

 it upon me to decide. 



The most remarkable metamorphoses of 

 compact calcareous strata, however, according 

 to liCopold von Buch's able observations, are 

 to be seen in the Southern Tyrol, and among 

 the Italian slopes of the Alps, effected princi- 

 pally by the intrusion of dolomitic masses. 

 The metamorphosis of the calcareous rock 

 here proceeds from fissures, which traverse it 

 in all directions. The clefts are everywhere 

 covered with rhomboids of magnesian spar ; the 

 whole formation indeed, without stratification, 

 and without a vestige of the fossils which it 

 formerly included, then consists exclusively of 

 a granular aggregation of dolomitic rhomboids. 

 Talc leaves and transverse fragments of ser- 

 pentine lie here and there dispersed through 

 the new-fashioned rock. In Fassathal, the dolo- 

 mite rises perpendicularly in the form of smooth 

 walls of dazzling whiteness to the height of 

 several thousand feet. It forms pointed coni- 

 cal hills, which stand side by side in great num- 

 bers without touching one another. Their 

 physiognomical character brings to mind that 



! sweetly fantastical mountain landscape with 

 I which Leonardo da Vinci has ornamented the 

 back-ground of his portrait of Mona Lisa. 

 I The geological features which we are here 

 portraying excite the imagination as well as 

 reflection ; they are the work of an augitic por- 

 phyry, which has intruded and produced its ef- 

 fect, by upheaving, shattering, and transform- 

 jj^g^ass) rp^g dolomitizing process is by no 

 means regarded by the gifted inquirer who first 

 pointed it out as an imparting of magnesian 

 earth by the black porphyry, but as a change 

 effected contemporaneously with the protrusion 

 of the injected rock into extensive fissures fill- 

 ed with vapour. It remains for future inquiries 

 to determine in what way the transformation 

 is effected when the dolomite occurs in beds 

 between limestone strata, without contact with 

 the endogenous rock, where the conduits of 

 Plutonic influences lie concealed. But it is not 

 perhaps necessary, even here, to take refuge in 

 the old Roman saying, according to which 

 " much that is like in nature has been produced 

 in totally different ways." If in an extensive 

 district of country, two phenomena, viz., the 

 protrusion of melaphyrO; and the alteration in 

 crystalline texture and chemical constitution 

 of a compact calcareous rock, always go to- 

 gether, then may we, with some reason, con- 

 jecture, that in cases where the second phe- 

 nomenon presents itself without the first, the 

 seeming contradiction in the non-fulfilment is 

 connected with certain conditions accompany- 

 ing the occult principal cause. Should we 

 question the volcanic nature of basalt and its 

 state of liquefaction through fire, because a 

 few rare instances have been met with in 

 which dykes of this substance traverse carbo- 

 niferous sandstone and cretaceous strata, with- 

 out the coal being deprived of its bitumen, the 

 sandstone reduced to the state of frit, or the 

 chalk being turned into granular marble"? 

 Where we meet with even a twilight glimmer, 

 with the faintest trace of a way in the obscure 

 region of mineral formations, we must not 

 thanklessly reject both, because there is still 

 much unexplained in the relations of transition 

 from one rock to another, and in the isolated 

 interposition of altered between unaltered 

 strata. 



Besides the transformation of compact cal- 

 careous carbonate into granular limestone and 

 into dolomite, there is a third metamorphosis 

 of the same deposit, which must here be ad- 

 verted to, and which is attributable to the vol- 

 canic eruption of sulphuric-acid-vapours, in 

 primeval epochs. This transformation of lime- 

 stone into gypsum is connected with the pene- 

 tration of rock-salt and sulphur (the latter pre- 

 cipitated from watery vapour charged with the 

 mineral). In the lofty chain of the Andes of 

 Quindiu, far from all volcanoes, I have myself 

 observed this precipitate within fissures in 

 gneiss, whilst the sulphur, gypsum, and rock- 

 salt of Sicily (Cattolica, near Girgenti) belong 

 to the newest secondary strata, or to the chalk 

 formations(=*"). I have farther seen fissures 

 filled with rock-salt, in quantities that some- 

 times tempt the people to engage in an illicit 

 traffic in the article, in the edge of the crater of 

 Vesuvius. On both slopes of the Pyrenees it 

 is impossible to doubt the connection of diorit- 



