47 



the largest transverse bases to the south will be propelled north- 

 ward at a greater rate than the others. (Plate XII.) 



Having lately made a very extensive investigation of the prin- 

 cipal mines of Cornwall, Wales and Ireland, with a view of in- 

 stituting a comparison between them and those of America, this 

 part of our subject was carefully attended to, and the result has 

 fully confirmed our previous opinion that the greater number of 

 the veins on the large scale have been " heaved " and filled simul- 

 taneously. The splits, generally speaking, are older than the 

 transverse fractures. The mines of Flintshire are referred to as 

 one instance out of hundreds which may be mentioned, where 

 the transverse cracks are confined within the limits of the me- 

 ridional strips. The cause of the meridional 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 lon- 

 gitudinal movements, and the other to transverse actions. 



CHAPTER VIII. 



MINERAL VEINS, THEIR MODE OF FILLING, AND THE 

 GENERAL CHARACTER OF THEIR CONTENTS. 



Bestdes the conflicting opinions respecting the origin of mine- 

 ral veins, much confusion has also arisen from the very loose 

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

 which they apply, in fact, to almost any species of mineral de- 

 posit which affords a foundation for mining operations, however 

 widely it may differ from the definition of these terms in a me- 

 chanical sense. To avoid this confusion, and to render the opi- 

 nion 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 strongly saturated with 

 minerals in solution, in a state favourable to chemical action, 

 and having a free motion through the pores of the rocks in obe- 



