538 C. CALLAWAY Olf A SECOND PRECAMBEIAN 



cular of the Lilleshall series with the " baked rocks " of the Here- 

 fordshire Beacon. 



I may state, though the fact is not of much value as evidence of 

 correlation, that the intrusive doleritic rocks which break up through 

 the Malvern felspathic series can be exactly matched in the Wrekin 

 and Caradoc chains. I refer especially to a dark green rock, with 

 amygdaloids of radiated * epidote, which is common at Caer Caradoc, 

 and to a coarser variety of a lighter colour which is abundant 

 further to the north-east. 



Professor Bonney (note 2) identifies as possibly an intrusive 

 quartz-felsite a doubtful-looking rock associated with the Malvern 

 hornstone. 



The relations of the two Precambrian formations at Malvern at 

 once suggested to me the sequence at St. David's, and I shortly 

 afterwards hinted the correlation to the Chester Natural-History 

 Society. Great caution must, however, be used in comparino- such 

 distant groups. I have long been disposed to consider the felspathic 

 series in Shropshire, or at least the Lilleshall group, as representing 

 the Pebidian. The lithological resemblances to the St.-David's 

 rocks are very close, and the deposits in both areas are due to vol- 

 canic action. If the Lilleshall series is Pebidian, then the horn- 

 stones at the Herefordshire Beacon are Pebidian. It is also of 

 importance to notice that these "baked rocks" can hardly be 

 distinguished in hand-specimens from some of the St.-David's rocks, 

 especially those which occur at Nun's Well (note 4). 



But the correlation of the central ridge at St. David's (Dimetian 

 of Hicks) with the Malvern axial ridge is not so evident. The 

 Malvern series is almost exclusively gneissic, foliation is well 

 marked, and hornblende abounds. In the St.-David's axis gneiss 

 is absent. Having searched the series from top to bottom, with the 

 assistance of Dr. Hicks's sections, I have been unable to detect 

 schist of any kind, the "quartz-schists" originally described being 

 really quartzites and granitoid rocks. On the other side we may 

 set the fact that these granitoid rocks are very similar to the 

 " granite " so largely developed in Swinyard's Hill, the Worcester- 

 shire Beacon, and the North Hill. In the present state of our 

 knowledge I cannot venture to express a more definite opinion. 



Professor Bonney, F.R.S., has independently observed the Pebi- 

 dian rocks of Malvern, and he permits me to say that he agrees 

 with me in my general conclusion as to their age. The following 

 microscopic notes are kindly furnished by him : — 



" (1) The prevailing type at the Herefordshire Beacon. — A rock 

 of sedimentary origin. A ground-mass of very finely granular aspect, 

 composed of earthy matter thickly interspersed with extremely 

 minute microliths, probably of felspar, through which are scattered 

 a few rather larger fragments of felspar, or quartz, or both ; some 

 minute epidote is also present. The specimen belongs to a type 



* This is probably the " actinolite " of Murchison (' Siluria,' 1867, p. 65, 

 note). I am indebted to Mr. Allportfor the identification. 



