REPORT ON MINERAL VEINS. 9 



beds, of whatever thickness they occur, have, on the contrary, 

 a similar direction with the strata of the rock, and instead of 

 crossing, run parallel with them : this forms the characteristic 

 difference." 



Playfair says : " Veins are of various kinds, and may in ge- 

 neral be defined, separations in the continuity of a rock, of a 

 determinate width, but extending indefinitely in length and 

 depth, and filled with mineral substances different from the 

 rock itself. The mineral veins, strictly so called, are those filled 

 with sparry or crystallized substances, and containing the me- 

 tallic ores." 



Mr. Carne says : " By a true vein I understand the mineral 

 contents of a vertical or inclined fissure, nearly straight, and 

 of indefinite length and depth. These contents are generally, 

 but not always, different from the strata or the rocks which the 

 vein intersects. True veins have regular walls, and sometimes 

 a thin layer of clay between the wall and the vein ; small 

 branches are also frequently found to diverge from them on 

 both sides." 



Mr. Carne mentions other veins, which he distinguishes from 

 the true ones as being shorter, crooked, and irregular in size ; 

 he considers these to have formed in a different manner : but 

 this will be discussed hereafter. 



These definitions seem to me to be sufficient for our pur- 

 pose ; but it may be advantageous here to introduce some 

 further description of circumstances connected with veins, and 

 to explain the terms usually employed to describe them. 



Being tabular masses, generally of no great width, any one 

 will, whether vertical or inclined, present at its intersection 

 with the surface a line nearly straight : this may be from north 

 to south, or from east to west, or in any intermediate course. 

 This is usually called the direction ; by miners frequently the 

 run of the vein, or the course of the vein, and is denoted by the 

 points of the compass it may cross. 



The length, as Werner states, is indefinite, it being doubtful 

 whether any vein has been pursued to a perfect termination. 



The tabular mass, again, may be either vertical to the plane 

 of the earth's surface, or may deviate from this position by in- 

 clining to one side or the other of the perpendicular. This 

 deviation is called the inclination of the vein ; by the Cornish 

 miners the underlie. It is measured by the angle made with 

 the perpendicular ; and as the dip will be to one side of the 

 direction, the latter being known, the other is easily expressed. 



The depth to which veins descend into the earth is unknown, 

 as well as the length, and for the same reason. 



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