632 ME. H. H. AENOLD-BEMROSE ON THE MICROSCOPICAL [JN~OV. 1 894, 



The upper dolerite may be traced for several miles. I cannot say 

 whether this tuff is merely local or underlies the upper dolerite 

 throughout its extent, as I have been unable to visit the district 

 since I found the tuff. 



We have here, resting on the ordinary limestone of the district, 

 ■ an ashy limestone, denoting a slight fall of volcanic ash during the 

 deposition of the limestone. This is followed by a lava-flow, that 

 again by a shower of coarse ash, and the whole by a lava-flow, which 

 extends over a large area. 



Cracknoivl House, Bahewell, Outcrop 34. — There is no good 

 exposure. In the valley below Cracknowl House, small patches of 

 red soil are seen on the eastern side. They contain small lumps 

 of the rock, many of which would not be seen except for the 

 rabbit-burrows. The rock is much decomposed : the lapilli are 

 very much altered and of a red colour, containing here and there 

 a much altered felspar-lath and iron oxide. An included block 

 (sp. gr. 2-44) contains olivine replaced by a mineral which gives 

 aggregate polarization, probably felspar or quartz, and felspar-laths 

 of two generations, the smaller ones being often curved, bifurcated 

 and ragged, and frequently giving parallel extinction. The ground- 

 mass has a slight action on polarized light. Quartz sometimes fills 

 the vesicles. 



Ember Lane, Outcrop 39. — Starting at the Bonsall end of Ember 

 Lane, we meet with the tuff on the left-hand side soon after the 

 turn from N.E. to E. It is exposed for about 200 yards in the bank, 

 and in a field on the left. It might at a little distance be taken for an 

 ordinary limestone, but, on closer examination, is found to be a lime- 

 stone with large lapilli embedded in it, which stand out in relief 

 when the rock is weathered. Specimens abound in the walls. 

 Proceeding up the lane it passes into a bedded ash, which is seen 

 to contain pebbles of limestone just before we reach a small shed. It 

 is difficult to make out the bedding, but if the dip corresponds with 

 those of the limestone taken at Cromford, and between that place and 

 this locality, the ash lies above the ashy limestone, and is succeeded by 

 a dolerite-flow seen near and beyond the shed. It is vesicular, and 

 the olivine and felspars are much altered. If these conclusions as to 

 the dip are correct, we have here limestone containing many lapilli, 

 or an ashy limestone, passing upwards into a bedded ash, and this 

 succeeded by a lava-flow. This dolerite covers a large surface on 

 Masson Hill, and is an olivine-dolerite containing in places augite 

 in grains, and in other places augite in ophitic plates. 



Mapping the toadstone from the 1-inch map on to the 6-inch 

 (which is not a very accurate method, as some of the details must 

 inevitably be exaggerated on the former scale), it will be found that 

 the toadstone-outcrop passes through places where the dolerite and 

 ash occur, but not through those where the ashy limestone occurs. 

 The latter is on an inlier (assuming the dip previously mentioned 

 to have been correct) of limestone between the 700 and 900-feet 



