406 



G. When the same lode is dislocated by various slides, do all the 

 latter throw it to the side of the greater angle, or all towards that of 

 the smaller ; or some to one, and some to the other ? 



In Huel Peevermine are two lodes and two slides ; both the lodes 

 are thrown down by one of the slides, and towards the greater angle ; 

 but one of the lodes,(a) on coming in contact with the other lode (6) 

 is thrown upwards or towards the smaller angle, and the same lode 

 (a) on meeting the slide (d) is again thrown upwards or to the smaller 

 angle. 



7. When various veins are thrown by the same slide, does it throw 

 them all upwards or all downwards, or some upward and some 

 downward ? 



In Huel Trevaunance mine some of the veins on coming in contact 

 with others are thrown down ; but one of the veins (a) on coming in 

 contact with the vein (/) is thrown upwards ; and the vein (6) on 

 coming in contact with the vein (/) is also thrown upwards, as is the 

 vein (f) on coming in contact with the vein (e). 



The author having thus " compared the general rules, which are so 

 frequently discussed,with facts," says, "Notwithstanding there are nu- 

 merous exceptions, it may be assumed that where across vein is found 

 to have heaved two or three lodes towards one hand, the miner will not 

 often be very far wrong if he excavate in the same direction to recover 

 a dislocated portion of a fourth ;" and the author further observes, 

 that he shall not be surprised if a different rule be found to prevail in 

 the districts where tin abounds, from that which obtains in a copper 

 country. He next proceeds to combat the received opinion, that all 

 interruptions or intersections in mineral veins are the effects of dis- 

 turbances, and that the order of intersection of the various veins is 

 the index of their relative age. 



He states that the only extraneous evidence of motion in veins is 

 the existence of slickensides ; but he says, that in Huel Robert mine 

 the slickensides traverse the substance of the vein in every direction, 

 and in almost every possible variety of form ; that in many other 

 instances he has seen on the plane surface very considerable promi- 

 nences ; that the striae were marked not only on the plane surface, but 

 also on the elevated portions ; that many of the striae on the walls of 

 the veins are converging, and that in numerous instances on opposite 

 sides of the same vein they dip different ways. 



The author then enters upon the inquiry whether the phenomena 

 of intersections and dislocations are explicable on the assumption of 

 motion. He states that horizontal motion will not account for a vein 

 being heaved to the right by one vein and to the left by another, or even 

 both the same way but to different distances. With respect to oblique 

 motion he says, that there are many instances of a lode being heaved 

 towards one hand at one depth and to the opposite at another depth • 

 and lastly, with respect to vertical motion he says, that if two lodes, 

 dipping the same way, be dislocated by the same cross-course, they 

 will be heaved towards the same hand, but if they dip different ways 

 they will be heaved to opposite hands ; he, however, states, that at 

 Huel Trenwith mine two veins dipping different ways are traversed by 



