HOCHSTETTER — GEOLOGY OF CARLSBAD. 13 



now decided by Prof. Bischoff's theory, and its experimental demon- 

 stration by Struve. 



The controversy concerning the Carlsbad granites has not yet been 

 brought to a satisfactory conclusion. M. von Hoff (1825) con- 

 sidered the coarse-grained and the fine-grained varieties of Carlsbad 

 granite to have been contemporary in their origin ; and this able ob- 

 server was the first who referred to the existence of a deep and broad 

 fissure, the result of volcanic action, and filled up with granitic brec- 

 cia. All the Carlsbad springs rise to day along this fissure, which 

 is known by the name of "von Hoif's line." 



M. von Warnsdorff (1846) considered the two varieties of granite 

 to have been produced at different periods, intimately connected with 

 the origin of the springs themselves, as these latter issue out exactly 

 on the limiting plane between the coarse-grained, or older, and the 

 fine-grained, or younger granite. The Schlossberg of Carlsbad is 

 not a granitic breccia, but a solid granite-mass, traversed with nume- 

 rous veins of silex deposited by the springs in the form of hornstone. 

 This opinion of M. von Warnsdorff' s is now pretty generally accepted, 

 as being confirmed by previous and later observers ; but his views 

 relating to the different ages of the Carlsbad granites are still not 

 quite assented to. 



Dr. Hochstetter, after a careful examination, came to the following 

 conclusion. The granitic rocks of the Tepl Valley, near Carlsbad, 

 form a portion of an extensive granitic mass", evidently of an eruptive 

 character, stretching from Marienbad through the whole of the Carls- 

 bad mountains, and far into the interior of Saxony beyond the Erzge- 

 birg. This granite is undoubtedly younger than the crystalline 

 slates surrounding it, and is characterized by abundance of tin- ore. 

 It varies in its grain frequently throughout its range ; near Carlsbad 

 the fine-grained variety a prevails on the right bank of the River 

 Tepl, whilst the left bank is chiefly occupied by the porphyritic fine- 

 grained variety 6, which contains the well-known twin-crystals of 

 felspar of Elbogen. The bottom of the Tepl Valley, as well as the 

 declivities immediately bordering it, are composed of a third variety 

 of granite, c, hitherto thought to be identical with a or b ; but which 

 ought to be carefully kept distinct in thoroughly investigating the 

 geology of the Carlsbad district. The last-named variety has a por- 

 phyroid aspect, its chief mass being fine-grained like the variety «, 

 but having interspersed isolated crystals of felspar and quartz, or 

 larger aggregations of scaly mica. In other localities, for instance, 

 at Schellerhau near Altenberg, in the Erzgebirg, this variety passes 

 into genuine porphyry. Its component minerals are potash- and 

 soda-felspars, black and white micas (the last probably containing 

 lithia), and quartz, both crystallized and uncrystallized ; while the 

 variety 6 is a compound of potash-felspar, black mica, and quartz. 



The differences in the mode and result of decomposition are still 

 more striking. The varieties a and b easily decompose into gravel, 

 the large felspar-crystals of b remaining unaltered. In the variety c, 

 the decomposition commences with these crystals, which are gradually 

 reduced into a yellowish-green steatitic or a reddish-brown earthy 



