THE 



GEOLOGICAL MAGAZINE. 



No. LXVI.— DECEMBER, 1869. 



(D:RXC3rXlSrJi^Xj -A-Z^TIOXjIEIS. 



I. — Banded and Brecciated Concebtions.^ 



By John Euskin, LL.D., F.G.S. 



[PLATE XIX.] 



WHEN we find at the sides of veins, the veinstone rent into 

 laminae, as I tried to represent in Plate XX. of Vol. IV. it is 

 easy to think of the fracture as violent, and of the disruption of the 

 vein as sudden. 



That, at least, this disruption must have been exceedingly slow, 

 and that as ic took place the rent must have been filled by contem- 

 porary crystallization, is I think evident in the instances figured, 

 and in the great number of cases which they represent. 



And as I continue my inquiry, it becomes more and more ques- 

 tionable to me whether there has in such cases been disruption at all. 

 For the more I endeavour to read Nature patiently, the more I find 

 that she is always trying to deceive us while we are impatient, by 

 pretending to do things in ways in which they never were done, and 

 making things look like one another, which have no connection with 

 each other. 



For instance, in Eig. 1, which 

 rudely sketches a piece of Cornish 

 hornstone, it would seem at first 

 sight that the detached black and 

 white bands were pieces of a band 

 once continuous, but which had 

 been broken up, and re-cemented 

 in disorder. And if, on a large 

 scale, we had met with the fault 

 in almost exactly coincident beds, 

 to which the arrow points, we 

 should have had little doubt of 

 their former continuity. But in this stone they have never been in any 

 other than their existing position, any more than the two upper 

 beds on the left, of which one is an entirelj'' undisturbed branch 



1 For former papers see Geol. Mag., 1867, Vol. IV. pp 337 aud 481 ; also 1868, 

 Vol, V. pp. 12, 156, and 208. 



VOL. VI. NO, LXVI. 34 



Fig. 1. 



