WATSON— NOTES ON METALLIFEROUS SADDLES. 



369 



tlie nature of tlieir ore contents, and, partly on tliis account, it has 

 been remarked at tlie commencement of tliis notice that the saddles 

 must not be classed indiscriminately with, but rather must be consi- 

 dered apart from, the general vein-system of the districts in which 

 they occur. Of course the separation cannot rest alone on the ground 

 of a change in the description of the ore, since many such changes, 

 and often from lead to copper, frequently occur in depth in true veins. 

 The real distinction lies in the mechanical position of the ore, which, 

 it would seem, gives a classification for the saddles between veins and 

 bedded deposits ; and this arrangement will be further confirmed if, 

 considering that the latter mostly comprehend mineral accumulations 

 introduced from above, and the former those injected from below, the 

 agency of the lums be regarded in a two-fold light — first, as 

 originally giving passage to copper-bearing solutions, with which 

 their other mineral contents were at one time largely impregnated ; 

 and, secondly, by afterwards permitting a free electrolysis of the 

 salts by which the copper was determined to the fissures in the 

 saddles, and by then, or after, acting chemical changes resolved into 

 sulphurets (copper pyrites) as now found.* Thus conceived, the 

 segregation of the ore in the saddles is a special phenomenon, and 

 deserves, as I hope I may have succeeded in some measure, at least, 

 to show, a separate and attentive consideration at the hands of phy- 

 sical geologists. It is not to be confounded with what in Flintshire 

 and elsewhere in the mountain-limestone mining-districts are termed 

 " flats," or " flat veins," notwithstanding that it more nearly resembles 

 those descriptions of deposits than any others. Still it is widely 

 difierent, since as on one hand flat veins, as their name implies, are, 

 comparatively speaking, horizontal veins, and often occupy a plain 

 corresponding irregularly with the stratifications, so, on the other 

 hand, the constant position of the ore in certain beds, as well as cer- 

 tain parts of those beds, is, beyond all doubt, the distinguishing 

 peculiarity of the general phenomena of the saddles. 



In the foregoing observations I have endeavoured to describe as 

 nearly as possible the average of the appearances presented by the 

 bearing beds of the Ecton district in the limestone ; but, as before 

 mentioned, the same phenomena are observable in the Upper Lime- 

 stone shales. They do not, however, merit any separate description 

 beyond the statement that they are similarly mineralized, are equally 

 traversed by lums, and have the same mechanical relations with the 

 neighbouring veins and with the associated strata. 



* Wliere galena is tlie associated ore, copper seldom occurs in any other form 

 tlian as copper pyrites, a fact wortliy of remark in comiection with the para- 

 genesis of metallic minerals. 



VOL. III. 



