Modes of Occurrence of Ores. 31 



ready discussed occur, though not exclusively, the venigenous 

 (i. e. small, irregular, tabular) repositories are sometimes con- 

 fined to certain zones or regions, which, when limited by two 

 plane surfaces, bounding them entirely or almost entirely, 

 and when these tabular regions lie conformably to the struc- 

 ture of the rock and mountain-masses, may be viewed as beds 

 more or less branched, or, when they intersect that structure, 

 may be regarded as more or less branched veins. Sometimes 

 such a region or zone is distinguished in the mountain-mass in 

 which such appearances present themselves, by the nature of 

 its rock, inasmuch as variations in its structure may be re- 

 marked, or it occurs in such a condition as is termed a more 

 or less advanced state of decomposition, disintegration, or 

 weathering, and which is attributed to a change produced 

 subsequently to the original formation. When such a region, 

 especially when it is not metalliferous, lies conformably to 

 the general structure, it is generally termed a rottenness (eine 

 Fdule), a clay fissure (ein Lettenkluft), &c. (at least what 

 are termed promising appearances come under this denomina- 

 tion) ; but if it intersect the structure, it is regarded, when 

 without ore, as a barren rock (taube Gedein), or clay vein 

 (Ltttengang), of which the slate mountains afford remarkable 

 examples. Sometimes, however, such veins ought not to be 

 neglected ; for it has often been observed that from them there are 

 developed vein-like formations, and even extensive and wide veins, 

 which not un frequently prove rich and of mining importance. The 

 Erxgebirge, both on the Bohemian and Saxon sides, contain ex- 

 tremely remarkable instances of this feature. In mountain- 

 masses in which there is no slaty structure present or perceptible 

 (which are no£ stratified, according to the usual mode of expres- 

 ssion), the nature of these repositories is determined by the dif- 

 ference of their direction, and by the general relations of super- 

 position, that is to say, we so determine whether they are to be 

 regarded as beds or veins. Various copper-ores (that is mine- 

 rals generally which contain copper, and which are used as 

 ores of copper , sometimes cinnabar, more rarely some others, 

 are the metallic substances found in these repositories, here 

 and there accompanied by the so-termed vein or bed-stones, 

 especially whon they are in the form of beds ; and tho abovo 





