4Q^ M. Von Buch on Gabbro: 



years the causes of destruction which the movement of a 

 large town brings with it; the great hardness and peculiar 

 tenacity of gabbro, renders this pavement at present very 

 superior to that of all other capitals. It is quarried at 

 Langenlois, near Crems, in Lower Austria; there are no 

 data upon the geology of this country, but it is known that 

 a great quantity of serpentine rocks, mixed with different 

 minerals, and, even as it appears, with green diallage, occurs 

 on the left bank of the Danube, near Gottweig, and not far 

 from Crems.* 



M. Esmark had observed, in 1802, that the mountains of 

 Thron, situated in the eastern part of Norway, between 

 Rorass and Fordel, elevated 4000 feet above the sea, were 

 formed of a peculiar rock, composed of felspar and a sub- 

 stance which resembled hornblende without being horn- 

 blende. 



In 1806, M. von Buch found gabbro on the western side 

 of Norway, three miles to the south of Bergen. It is com- 

 posed of felspar, and grey diallage, without jade. It con- 

 stitutes the whole of a branch of mountains, extending for 

 several leagues on the right side of Saumangerfiord, and often 

 forming precipitous rocks. Tlie mixture is never large 

 grained ; the grain is sometimes so fine that the diallage can 

 with difficulty be distinguished ; but elsewhere, and more 

 particularly on the side of a lake near Kallandseid, the 

 crystals of diallage are often the size of the fist, their greenish 

 grey colour, and the lustre they exhibit on a single large 

 surface, easily distinguish them from hornblende, beds of 

 which occur near in'arglllaceous slate. Gabbro reposes here 

 on primitive argillaceous slate that rests on gneiss. 



The same relative position occurs in the neighbourhood of 

 the North Cape, in the isle of Mageroe. The rocks are 

 there so much exposed, that the changes that take place in 

 their nature are easily observed : and a complete geological 

 passage may be traced from the primitive schist to large 

 grained gabbro. The nearest schistose rocks that surround 



* Stiitz oryctographie von Nieder CE>terreich, p, 228. ^ 



