RELATIVE ANTIQUITY OF VEINS. 409 



flukans. But all the east-and-west lodes are not of the same age, the 

 tin being older than the copper ; neither are all the east-and-west tin 

 veins of one age, for those that underlie to the north are generally 

 traversed by those that underlie southwards. These curious generalisa- 

 tions are not to be overthrown by particular discordances ; and they 

 are certainly supported by analogous though less varied occurrences 

 in other countries. 



Directions of Veins of Different Antiquity. The general order 

 of their dates may be thus expressed : 



1. Oldest, east-and-west tin veins underlying to the north. 



2. East-and-west tin veins underlying to the south. 



3. East-and-west copper veins generally east to south. 



4. Oblique or contra copper veins, generally east 30 to 45 south. 



5. Cross courses not metalliferous, north and south. 



6. Copper lodes of more recent date and lead veins. 



7. Cross flukans or clay dykes nearly north and south. 



8. Slides in all directions, but generally east and west. 



The porphyritic and other dykes called elvan courses are very 

 generally divided by the veins, and seem to be of greater antiquity. 

 Werner observed this geographical relation of mineral veins, and stated 

 the two following cases. In the mining district of Freiberg are two 

 classes of veins very different from one another. One of these classes 

 consists of veins which run from north to south. The veins of this 

 group contain lead glance, black blende, iron, copper, and arsenical 

 pyrites, quartz, and brown spar. This is the oldest vein-formation. 

 The second class of veins, which always traverse the former, and are 

 never crossed by them, contains lead glance, radiated pyrites, heavy 

 spar, fluor spar, and quartz. They strike between the sixth and ninth 

 hours of the mining compass (east to south-east). 



The mining district of Ehrenfriedesdorf contains veins of tin 

 and silver glance. The tin veins are always traversed by the silver. 

 The direction of the first is between the sixth and ninth hour (east 

 and south-east), that of the last from the ninth to the third hour (south- 

 east, south, south-west). 



Direction of Mining Districts. There is observed in some mining 

 districts another remarkable relation of metalliferous veins to geo- 

 graphical lines. Though in the North of England the most frequent 

 direction of the veins lies east and west, the mining districts seem 

 rather to be ranged in lines from north to south. The nature of this 

 relation will be more easily understood if we add that both in Corn- 

 wall and in Cardiganshire, where the veins are also most frequently 

 east and west, lines of greater productiveness range nearly north 

 and south across the bearing of the veins. These curious notices 

 suggest the inquiry whether the lines of productiveness are dependent 

 on any principal axis of dislocation or strain, or on the occurrence 

 of cross courses. The former case seems to be indicated by the 

 phenomena in the North of England. Perhaps the latter may be 

 more applicable to Cornwall. 



Connection of Fissures and Main Joints. It is certain that in 



