160 Mr Kenwood on the Phenomena of 



not anterior to it ; for it is scarcely possible to think that any 

 which had existed in the rocks previously to the formation of 

 the veins, would have been prolonged from each side through 

 the latter with such exactness. It cannot be doubted that the 

 contemporaneity of veins very much simplifies any idea of their 

 origin. 



When two veins, having different directions, meet horizon- 

 tally, one often intersects the other, the portions [of that cut 

 through, not being found exactly opposite each other, on the 

 different sides of the traversing vein, but by turning either to 

 the right or to the left hand. The right and left hands are fa- 

 miliarly employed by practical men in preference to the points 

 of the compass, as, on whichever of the divided portions we ap- 

 proach the intersecting vein, the heaved segment will be found 

 on the same hand. 



When veins intersect vertically in descent, this want of coin- 

 cidence is called a slide ; a few of these occur in many parts of 

 the county, but they are most common in St Agnes and Gwen- 

 nap ; whilst the heave is of almost universal occurrence, being 

 found of greater or smaller extent in every mining district of 

 Cornwall. 



A little consideration of the phenomena will shew that the 

 latter may occur alone, if the veins have a horizontal parallel- 

 ism, and the former only if horizontally at right angles ; whilst, 

 if there be any intermediate directions, at certain points in their 

 extent, one, and at others, the other of them will obtain. 



A great point in dispute is, were these opposite portions ever 

 united ? it being an axiom of Werner's, which has been adopt- 

 ed by all the advocates of these originating in mechanical dis- 

 turbance, " that a vein which is intersected or traversed by ano- 

 ther vein" " is older than the vein by which it is traversed." 



In this investigation we are not to consider that the pheno- 

 mena in question are their own explanations, or that the fact of 

 an intersection is a proof that they were ever united; it is evi- 

 dence of an independent nature we require. 



My distinguished friend Professor Phillips says, "How can the 

 geologists of Cornwall doubt the reality of those angular move- 

 ments, which have left such clear evidence as the fine slicken- 

 sides of some of their veins or fissures T If this acute observer 



