ERBYSHIRE f RCH/EOLOGICAL 



ATURAL MlSTORY SOCIETY. 



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Ettrcstoell ^ale €Utan*£. 



By George Fletcher. 



BOUT a mile from the railway station at Miller's Dale, 



near the lower road towards Tideswell, is a limestone 



quarry. To a casual observer it appears to be very 



uninteresting, but a geological eye discerns much that 



will afford valuable aid in elucidating the past physical 



geography of the district. 



I have said that it is a limestone quarry, but it contains a large 

 quantity of hard, dark-coloured rock, found in many other parts 

 of Derbyshire, interstratified with the limestone. This rock, 

 which occupies a comiderable portion of the quarry, presents 

 features of great interest. It occurs at Miller's Dale, Matlock 

 Bath, Ashover, Elton, and many other places in the county. The 

 different exposures present various points of difference, but all 

 resemble each other in certain distinguishing characteristics. For 

 example, the rock is crystalline in structure, and examination of a 

 thin section under the microscope proves it to be a volcanic lava. 

 This conclusion rests, not merely upon the nature of the crystalline 

 constituents of the rock, but upon what may be termed its macro- 

 scopic peculiarities and its mode of occurrence. Its mineralogical 



