174- ON THE MINERAL AND METALLIFEROUS [Ch. IX. 



course, it becomes so assimilated with the granite, that its 

 presence is only marked by short unconnected strings, and 

 even these, at the junction of the granite and the slate, are 

 entirely wanting. The northern extremity of the vein is 

 more regular, varying, however, from twelve to five inches in 

 thickness, and having an undulating course : as it approaches 

 the granite, it heaves a granite vein to the left, and five feet 

 farther on, ends in ramifications before reaching the granite ; 

 a fine open line, or seam of structure, continues for six feet, 

 which, next the granite, is in two or three places, for a few 

 inches in length, lined with minute crystals of quartz, but for 

 eighteen inches beyond these small veins, there is no signs of 

 strings, cracks, or continuations of any description: the 

 quartz vein is altogether obliterated. A little farther on, in 

 the direction of the southern extremity, two branches, or 

 distinct veins, run side by side, then both become obscure, 

 and again continue their course, as indicated in the plan. 

 The dip of this vein is not clearly shown, but it appears to 

 be nearly perpendicular : it is, throughout the greater part of 

 its course, distinctly separated from the rock by open seams 

 or walls ; but at several places, both in the granite and the 

 slate, it is most unequivocally united therewith by mineral 

 transitions ; these rocks also enter into its composition, and 

 the seams by which they are divided into concretions often 

 intersect the vein. 



On the rocky shores of St. Just, however, the veins are 

 frequently exposed for a considerable distance; and it is also 

 an important circumstance, that they are metalliferous, and 

 very many of them have been extensively explored. A vein 

 of this kind occurs at Forth Just, Cape Cornwall, the lode of 

 Little Bounds mine, and is what is technically termed a 

 master-lode, on account of its size and regularity. The 

 rough diagram (Jig. 13.) will show the bearings of this vein, 

 and of an adjacent elvan-course, or large granite-vein ; but it 

 must be remarked, that many parts of its course are obscured 

 by loose pebbles and boulders. 



