Geology and Magnetism. 523 



splits, generally speaking, are older than the transverse fractures. 

 The mines of Flintshire are referred to as one instance out of hun- 

 dreds which may be mentioned, where the transverse cracks are 

 confined within the limits of the meridional strips. The cause of 

 the meridonal splits intersecting the east and west cracks is not 

 from their being of a more recent origin, but owing to one series 

 being subject to perpetual longitudinal movements, and the other to 

 transverse actions." 



We give the following observations on veins entire from 

 the practical importance of the subject, no less than the 

 interesting view taken of it by Mr. Hopkins. 



u Eesides the conflicting opinions respecting the origin of mineral 

 veins, much confusion has also arisen from the very loose significa- 

 tion which is given by miners to the term vein or lode, which they 

 apply, in fact, to almost any species of mineral deposit which affords 

 a foundation for mining operations, however widely it may differ 

 from the definition of these terms in a mechanical sense. To avoid 

 this confusion, and to render the opinion which is here maintained 

 respecting their origin more clear, we shall distinguish them by 

 veins of fractures and split veins ; the former being more or less 

 east and west, and the latter north and south : transverse fractures 

 and meridional splits are to be considered as identical. We must 

 always bear in mind the fact, that the rocks are more or less strong- 

 ly saturated with minerals in solution, in a state favourable to 

 chemical action, and having a free motion through the pores of the 

 rocks in obedience to the polar force. Those who may wish to 

 know whether this is a known fact in England, may consult the 

 numerous experiments of Mr. Fox, who has proved the existence 

 of the subterranean currents and mineral salts in Corwall by re- 

 peated experiments. Indeed, to doubt this is equal to doubting 

 the meridional action of the magnetic needle ; the latter is the 

 effect of the same power. 



We have already observed that the meridional channels of rocks 

 contain different kinds of minerals, the fractures intersecting which 

 form what are called lodes or mineral veins ; we shall now consider 

 the nature of their contents. 



