Stratification of the Limestone District of Derbyshire. 131 



teen in number, which form together the great system of pa- 

 rallel veins characteristic of the district, is accompanied through 

 at least a considerable part of its course by a fault, 



8. A small system of parallel veins is sometimes found 

 independent of the general system, but having this character 

 in common with it, — that the common direction of the system 

 coincides with the particular dip of the strata in which it is 



formed. 



9. Though fissures, I have no doubt, accompany the trans- 

 verse as well as the longitudinal faults, they much more rarely 

 become good mineral veins, and I know of none that are con- 

 tinuous as such for any considerable distance. Instances, how- 

 ever, are not wanting of productive veins of this class. 



10. Many small veins exist in the direction of which I have 

 detected no general law. These cross veins, however, are for 

 the most part incomparably smaller as fissures than the great 

 E. and W. veins above mentioned. 



11. All the great springs of this district are found in con- 

 junction with the great faults. I do not at this moment recol- 

 lect an exception to this rule ; for, I believe, in every instance 

 where I observed a powerful spring I had independent evidence 

 of the existence of a great fault. The water is also generally 

 observed to proceed from the upper surface of the toadstone, 

 as might be expected from the circumstance of its being unable 

 to penetrate it. The circumstances attending the positions of 

 these springs, when carefully examined, offer a curious corro- 

 boration of the fact of the regular interstratification of the 

 toadstone beds. 



12. I have observed no indications of a central point from 

 which the toadstone might be conceived to have flowed as from 

 a crater; nor have I yet observed any very distinct appear- 

 ances of an altered state of the limestone at its junction with 

 the toadstone. My attention, however, has not yet been so par- 

 ticularly directed to this latter point. Should any of your 

 readers have detected instances of this kind, I should feel 

 obliged for any information respecting them. 



We may remark that this view of the subject does not in- 

 volve, as an essential part of it, the supposition of any great 

 and extensive denudation, but merely that local and partial 

 operation of denuding causes which must be recognised in al- 

 most every district. 



I remain, Gentlemen, yours, &c. 



W. Hopkins. 

 St. Peter's College, Cambridge, 

 July 18, 1834. 



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