356 



PJROCEEDIN'GS OF THE GEOLOGICAL SOCIETY. [JunO 19, 



XIX. From a " dyke " in the Hollybush Sandstone at the south- 

 west base of Midsummer Hill : dark-coloured. 



XX. From the same ; light-coloured, magnetic. 



Both these specimens have the appearance of porphyritic lava. 

 Hornblende, imperfectly crystallized, occurs more abundantly in XX. 

 There are also a few minute red crystals resembling orthoclase. 

 There is some magnetic oxide of iron disseminated through both 

 rocks ; but in the darker portion the greater part of the free oxide 

 of iron is the protoxide : in the lighter portion, which is of a reddish 

 colour, the magnetic oxide predominates. 



A mass of felstone on the north side of the east cone of Bagged Stone 

 Hill has the same constitution as these rocks ; but it differs in its 

 physical characters and mode of occurrence. It was probably formed 

 by a mechanical deposition of the products of volcanic action. "With 

 the analysis of this rock I give one of a fragment from the summit 

 of Ben Kevis, which in composition closely corresponds with it and 

 with the eruptive rocks of the Hollybush period. 





















nS 













© 







SUD 



rt 







c3 



i+H 



CM S 



^ ^ 





o3 



M . 



03 





1 



i 





II 



O 



o g 









.2 S 



XXI. 



59-45 



20-50 



302 



trace 



0-25 



3-54 



1-15 



1-18 



10-91 



XXII. 



58-70 



21-19 



3-80 



0-17 







2-97 



1-09 



1-61 



10-47 



XXI. Felstone, from the north side of the summit of the east 

 cone of Bagged Stone Hill. 0=2-614. 



XXII. Dark-coloured rock, weathering white, from the summit 

 of Ben Kevis. 



The Hollybush Sandstone includes some thin beds, apparently 

 formed by the deposition of felspathic ash. One of these may be 

 observed on the east side of the quarry, at the south-west base of 

 Midsummer Hill, east of the eruptive rock, XIX. XX. It is, in part, 

 of the structure of sandstone, and in part felspathic, with traces of 

 epidote. These thin beds differ from those forming larger masses of 

 a later date, in being composed of a rock which is nearly a trisilicate. 

 Its composition is similar to that of portions of a lava-bed near Cas- 

 tle Morton Common, and to that of some grey sandstone on the hill 

 overlooking Little Malvern. 













% 







toD 







§ 



=3 





CM % 



^1 



6 



1 



1— 1 . 



§1 



00 ."rt 









IS 



"S '-' 



•ao 



*« 0^ 



^ 



s « 



,^ 1— 1 





xn 



'A 



d 



O 



o^ 



f-^ 



% 



^ 



< 



XXIII. 



64-20 



16-41 



6-45 



0-30 





1-32 





4-18 



7-14 



XXIV. 



67-78 



16-29 



1-21 









1-32 







2-04 



11-36 



XXV. 



67-99 



17-96 



2-30 



0-40 





2-11 



trace 



1-31 



7-93 



XXVI. 



65-43 



19-71 



3-77 









1-23 



1-13 



2-70 



6-03 



