366 . 



TRANS AC TIOH'S OP THE 



may be sometimes considered as contemporaneous with 

 those parts of the other veins in which they are met with, 

 although perhaps not always so with the rocks which 

 contain those veins. 



Veins of jasper occur in tin and copper lodes; are of 

 various colours, green, yellow, red and black ; they are 

 of small size, under one inch, and appear to have no re- 

 gularity of position or direction. 



Opal has been also met with, in the quartz matrix of 

 tin lodes ; sometimes the fire opal has been found thus ; 

 the lodes containing opal and jasper are in granite. 



Veins of fluor spar occur frequently as a vein stone of 

 metalliferous veins, and is often found with purple veins 

 of the same substance running through it in all directions. 



These are, then, most of the veins of whose contem- 

 poraneous formation there is the greatest probability. 

 It is not improbable, were the attention of miners more 

 directed to this subject, that additional ones would be 

 discovered, and more correct data than are now possess- 

 ed, aiford fresh light on this interesting subject. 



There is another class which are of such a character 

 as to render it difficult properly to designate them. We 

 should, however, place them under the head of doubt- 

 ful veins." This order will comprize all those whose 

 situation, appearance, and attendant circumstances, ren- 

 der it doubtful whether their formation was contempo- 

 raneous with, or posterior to that of the rocks which con- 

 tain them. 



Granite veins in the clay slate of Cornwall, have been 

 the subject of much discussion; and it would appear 

 that the more they are examined, the more difficult it 

 will be found to form any consistent theory respecting 

 them. So different are their appearance and attendant 

 circumstances, in different parts, that a very plausible 

 theory made with reference to the veins of one spot only, 

 will be found quite inconsistent with those of another. 



