Vol. 54.] NEAR THE HEREFOETDSHIEE BEACON. 557 



a cryptocrystalline matrix, which in ordinary light is flecked over 

 with probably an incipient development of epidote. I shall refer 

 again to this occurrence later on. In some cases, as Mr. Rutley has 

 already pointed out, there is perhaps in the arrangement of the flecks 

 evidence of an originally perlitic structure.^ Some specimens are 

 more glassy in habit, and may be called devitrified obsidian. 



The more basic rocks to which I refer under the name of ande- 

 s ites vary rather more, chiefly in respect of the presence or absence 

 of a ferromagnesian constituent and of porphyritic felspars. In 

 some cases the slide shows little but lath-shaped felspars. 



The excavations that were necessary for the new Reservoir were 

 looked forward to in the hope that some further light might be 

 thrown on this group. They were made in the ^ combe ' lying 

 between Tinkers Hill and Broad Down, and I drew attention 

 to them in Geol. Mag. 189-4, p. 48. The puddle-trench for the 

 embankment was cut in a very much shattered rock, in. which 

 there was so much calcite that at first it was supposed to be 

 Archaean limestone. Under the microscope, however, it is very 

 evident that the calcite is secondary and infiltrated (28).^ 



It was not, however, until the sides of the combe were cut into 

 that any distinct signs of bedding could be m ade out, and as the work 

 progressed they were gradually revealed. The strike is nearly 

 north-and-south, the dip from 40° east to nearly vertical at the 

 puddle-trench. Unfortunately the excavations were not carried far 

 enough west to uncover the junction between this series of rocks and 

 the crystalline main axis of the Malvern Hills. 



The bed that lay undermost, so far as seen, was of bluish-grey clay. 

 This appears to be derived from the decomposition of a felsite, 

 as the solid fragments show under the microscope all the charac- 

 teristics of that class of rock (242). Above this is a green 

 rock (203), which is considerably decomposed, and there is 

 infiltration of calcite ; but it agrees very well with Mr. Eutley's 

 description of the basalt at the back of Clutter's Cave and with 

 my slices of the rocks there. The felspars are lath-shaped ; the 

 ferromagnesian constituent is much altered. 



Above this is a red rock (202). The slices show 1 hat it is a fine- 

 grained tuff. Eastward and above this is a green rock (168). On 

 each side of the Reservoir appeared a very distinct bed of black clay. 

 The microscopic section of the rock shows that it is a basalt. 

 There is a large development of chlorite replacing augite. 



During the excavation it was interesting to note two conspicuous 

 rocks, one green (168), and the other red (117 «, 170), side by side. 

 The latter belongs to the bed next above. This bed is at the 

 bottom a fine-grained tuff, and has almost the appearance of having 

 been sorted by or deposited in water. Higher in this bed is a 

 coarse-grained tuff (210, 244, 260). There are in it fine felspar- 



1 Quart. Journ. Geol. Soc. vol xliii (1887) p. 499. 



^ The numbers iu parentheses refer to the slides in my cabinet. 



