Miscellaneous. 



453 



The limestone, in a half decomposed state, containing a great quan- 

 tity of white sand, enters into this formation in subordinate beds. In 

 some places this limestone decomposes to such an extent as to form a 

 white powder which covers the whole surface. 



Sandstone, small grained, of a dark colour, traverses this formation 

 also in beds, which alternate occasionally with those of the predomi- 

 nating rock. These beds of sandstone have only a thickness of 1 or 2 

 archines. 



The porphyry, which rises in the form of a mamelon, near the tem- 

 ple of Ba-or-Sy, three li to the north-west of that of Loun-Tzouan-Sy, 

 appears to have had some influence in the formation of this dolomite. 



This porphyry, of a deep red colour, gives out a strong smell of clay. 

 It has but little consistence, and its surface is fissured all over. 



The ferruginous red sandstone, which is divided into rhomboidal 

 faces by joints, ought likewise to be classed as belonging to the dolo- 

 mite formation. It does not constitute any considerable masses, and 

 is only found lying on the flanks of the compact dolomitic limestone. 

 The sandstone, in decomposing, forms an excellent soil for cultivation. 



One li to the north-west of Loun-Tzoun-Sy, a small outcrop of a 

 chloritic slate, having a coarsely foliated structure, is seen bordering 

 upon the dolomite, which disappears almost entirely under alluvial 

 clay. Its dip is very highly inclined, the beds being very irregular 

 and singularly contorted. Some traces of lime are found in it, but no 

 other minerals. 



The Western Mountains, as has already been said, are composed of 

 different rocks. Three formations are distinctly observed in them. 



1st, Diorite ; 2d, compact grey limestone, which appears to corres- 

 pond with the mountain or carboniferous limestone of England ; and, 

 lastly, the coal formation. 



A formation is besides observed, the independence of which is not 

 altogether demonstrated. This is a species of conglomerate intimately 

 connected with the diorite, and which will consequently be described 

 at the same time with that igneous rock. 



Dioritic Formation. — Diorite (greenstone) appears at the surface at 

 the village of San-Ourad-Yan, and extends in ascending the course of 

 the river Bourbouse to the village of Van-Pin-Koon, a distance of more 

 than 30 li. 



The diorite, small-grained, of a light green colour, is divided by 

 fissures, giving it the form of beds inclined about 15° to the east. 

 This rock is not very hard, except in its inferior portions; but as 

 it acquires elevation, it loses its granular texture, becomes friable and 



