180 Mr. Hen wood on the {Displacements) Heaves 



are brought into its vicinity, either in an opposing electrical 

 condition, or capable of becoming so, such free charge conti- 

 nues to exhibit its usual phaenomena, and is at all times resi- 

 dent only upon the surface of matter. 



On the occurrence of any body in the vicinity of the accu- 

 mulation of a sufficient magnitude, an amount ofjluid is dis- 

 placed from the latter in proportion to the contiguity of the 

 bodies ; and if the removal of force equals the accumulation, a 

 perfect polarization and neutralization with regard to all other 

 bodies of the primitive force is the result. 



Unneutralized electric fluid is at all times " free," and ac- 

 cording to the distance of the opposing force is the extent of 

 freedom of the fluid. 



XXIX. On the {Displacements) Heaves of Metalliferous Veins 

 by Cross-veins. (Part I.) By William Jory Henwood, 

 C.E., F.R.S., F.G.S. 



TN practical geology there is no point of greater importance 

 ■*- than the rediscovery of a metalliferous vein which has been 

 heaved by a cross- vein. 



In the series of papers, of which this is the first, I will en- 

 deavour to submit the results of my inquiries on this subject 

 in the mines of Cornwall and Devon. 



The result of every intersection must be either a simple 

 cutting through of one vein by the other, or a heave (displace- 

 ment). In the former case the portions of the intersected 

 vein occur exactly opposite to each other on either side of the 

 intersecting vein. In the latter this is not the case, but when 

 the traversing vein is approached along the course of one of 

 the severed parts, the other is found by turning towards the 

 right- or left-hand ; towards the greater or smaller angle. 



(I.) Intersections of lodes affording different ores by eross- 

 veins. — I have observed 233 intersections, of which 50 are of 

 lodes yielding tin ores only, 59 of lodes in which the ores of 

 tin and copper occur together, and 124 of lodes affording 

 copper ore alone. 53 of these intersections are simple and 

 unattended by heaves', of the remainder, 119 are heaved to- 

 wards the right-hand and 61 towards the left: 150 to the 

 greater, and 30 to the smaller angle. 



The relative proportions of the various phaenomena are as 

 follows, viz. 



per cent. 

 Of all the lodes the proportion intersected but not 



heaved is 22'7 



OfthetinMtt J8'0 



