SALMON — ON THE FORMATION OF ORE-YEINS. 



427 



WitlL these Oleni there also occurs the Agnostus ]jmformis, a fossil 

 which vre have already noticed in the Welsh beds, and as chai'acter- 

 izing the oldest Silurian schists and alum-slates of Sweden. 



"We have also at Whitesand Bay, in South Wales, the Cambrian 

 strata, overlaid by beds of flagstone containing the characteristic 

 Lingida Davisii ; and we onght not to omit to mention that the white 

 crystalline and fissured rock at Grantham, near Pontesford, in Shi^op- 

 shire, is penetrated by a vein of anthracite, small flakes of which are 

 also disseminated through the mass. 



It is difficult at present to account for the occurrence of this sub- 

 stance so commonly regarded in more recent deposits as of terrestrial 

 vegetable origin. This ancient anthracite may, however, have been 

 derived from sea- weeds, or indeed from land-plants, although no re- 

 mains of such have as yet been found in these lower rocks ; or, on 

 the other hand, its origin may have been due to accumulations of 

 animal matter. 



GEKERAL CONSIDERATIONS ON THE FOMIATION 

 OF ORE-YEINS. 



(Translated from the German of Professor Bernhard Cotta, of 

 Freiberg, ivith an Introductory Notice on the Study of Mineral 

 Veins and Metalliferous JDejposits, hy H. C. Salmon, Esq., Plymouth.) 



(Continued, from ]jage S96). 



YIII. Texture of Ore-Veins. — The varying texture of ore-veins 

 referred to towards the end of Prof. Cotta' s memoir may not be 

 intelligible without a short explanation. We find that the two ex- 

 treme textures of veins may be classed as (1) a cmnjoact texture, and 

 (2) a handed or layer-like texture, both of these of course having many 

 varieties, and passing into each other. The first is often characterized 

 by a hreccia-tQ-KivjoQ, that is by containing fragments — often very 

 numerous — of the neighbouring rock. The figure below shows an ex- 



