368 



THE GEOLOGIST. 



tliem are loaded with fossil debris, particularly tlie stems of encri- 

 nites. It may be argued that as the contorted beds occur at intervals 

 among the other beds, they must have possessed some peculiarities 

 that caused them to undergo such great mechanical changes, while 

 the other beds are comparatively unaffected. It may be answered 

 that this was probably the case, and that these beds, moreover, are 

 exposed by circumstances to a greater amount of compressing force ; 

 for it must be borne in mind that all the strata show more or less of 

 contortion, and that it is only in limited areas that the bearing beds 

 themselves exhibit the phenomenon in the utmost degree, inasmuch 

 DjS there is an almost undistinguishable difference in this respect 

 between these strata and the others at their crop*, as before observed. 

 The mentioning of these facts is necessary, lest it may be 

 thought that these contorted strata were formed and transformed 

 previously to the deposit of the overlying beds, against which sup- 

 position there is every evidence. 



But to return. During the re-emergence of the mass of the 

 strata, for which we have been supposing the changes above 

 imagined, we may conceive the dislocations and separations of the 

 beds, whether separately between themselves, as in the saddles, or in 

 whole masses, more or less vertically, as in the veins, to have 

 occurred. The complicated fissures forming the pipe-veins, with 

 their associated rake-veins, were in all probability formed simul- 

 taneously with the fissures in the bearing beds. It the same time, it 

 is likely that the great east and west faults called the " lums," were 

 of more recent origin, and formed by a wholly separate system of 

 dislocations ; and it may be taken that the saddle-beds are the lines 

 of least resistance, along which these last manifestations of the dis- 

 ruptive force displayed themselves. Moreover, there is great rea,son 

 for supposing that the infilling of the fissures and joints in the bear- 

 ing beds, with their cupreous contents, were effected through the 

 media of the lums which were thus formed. The lead, on the other 

 hand, was probably supplied to the pipe-veins through the agency of 

 their intersecting rake-veins, which continue to descend indepen- 

 dently of them to unknown depths, and are probably the channels 

 through which the plombiferous menstrua originally ascended. 



The parts stated at the conclusion of the last paragraph point to a 

 remarkable natural distinction between the saddles and the pipes in 



* The oiitcoming of the bearing-beds is recognized, among other appearances, 

 by the more crystalline character of the limestone, but with the exception of the 

 occasional presence of the peroxide of iron, there is nothing to indicate the 

 metalliferous condition which obtains in them elsewhere ; and, it may be, though 

 I have no positive knowledge of the fact, that their mifossiliferous state, as re- 

 marked in the text, is also only partitive. It is not difficult to imagine that the 

 intense scpieozing, necessary to produce the often fantastic contortions of the ore- 

 braring parts of these beds, would be sufficient to crush and obliterate any re- 

 mains oT oi i^anisms previously preserved, particularly if aided by any subsequent 

 nrrangriiuail hi the molocnlnr agglomeration of the rock, of which there is 

 abiiiidaiil e\ idciu'o in, at least, the productive portions of these strata. 



