252 COSMOS. 



the Altai Mountains, and at Las Trincheras, on the slope ol 

 the littoral chain of Caraccas,* I have seen granite divided 

 into ledges, owing probably to a similar contraction, although 

 the divisions appeared to penetrate far into the interior. Fur- 

 ther to the south of Lake Kolivan, toward the boundaries of 

 the Chinese province Hi (between Buchtarminsk and the 

 River Narym), the formation of the erupted rock, in which 

 there is no gneiss, is more remarkable than I ever observed in 

 any other part of the earth. The granite, which is always 

 covered with scales and characterized by tabular divisions, 

 rises in the steppes, either in small hemispherical eminences, 

 scarcely six or eight feet in height, or like basalt, in mounds, 

 terminating on either side of their bases in narrow streams.! 

 At the cataracts of the Orinoco, as well as in the district 

 of the Fichtelgebirge (Seissen), in Galicia, and between the 

 Pacific and the highlands of Mexico (on the Papagallo), I 

 have seen granite in large, flattened spherical masses, which 

 could be divided, like basalt, into concentric layers. In the 

 valley of Irtysch, between Buchtarminsk and Ustkamenogorsk, 

 granite covers transition slate for a space of four miles,! pen- 

 etrating into it from above in narrow, variously ramified, 

 wedge-like veins. I have only instanced these peculiarities 

 in order to designate the individual character of one of the 

 most generally difiused erupted rocks. As granite is super- 

 posed on slate in Siberia and in the Departement de Finisterre 

 (Isle de Mihau), so it covers the Jura limestone in the mount- 

 ains of Oisons (Ferments), and syenite, and indirectly also 

 chalk, in Saxony, near Weinbohla.§ Near Mursinsk, in the 

 Uralian district, granite is of a drusous character, and here 

 the pores, like the fissures and cavities of recent volcanic prod- 

 ucts, inclose many kinds of magnificent crystals, especially 

 beryls and topazes. 



2. Quartzose porphyry is often found in the relation of 

 veins to other rocks. The base is generally a finely granular 

 mixture of the same elements which occur in the larger im- 



* Humboldt, Relation Historique, t. ii., p. 99. 



t See the sketch of Bu-i-tau, which I took from the south side, where 

 the Kirghis tents stood, and which is given in Rose's Reise, bd. i., s. 584. 

 On spheres of granite scaling off concentrically, see my Relat. Hist., t. 

 ii-, p. 497, and Essai Giogn. sur les Gisement des Roches, p. 78. 



X Humboldt, Asie Centrale, t. i., p. 299-311, and the di-awings in 

 Rose's i2ee«e, bd. i., s. 611, in which we see the curvature in the layers 

 of granite which Leop. von Buch has pointed out as characteristic. 



§ This remarkable superposition was first described by Weiss in 

 Karsten's Archiv fur Bergbau mid Huttemcesen, bd. xvi., 1827, s. 5. 



