Rejjorts and Proceedings — Geological Society of London. 41 



decomposed. The stratified rocks of the district are indeed penetrated 

 by veins; but these consist of "■ granulite'''' (not granite), and they 

 ramify through both granite and sedimentaries alike ; in the former 

 they are called pegmatite, in the latter granulite proper. They 

 behave like true eruptive rocks, and are welded to the walls of the 

 adjacent phyllite, which they harden and modify at the contact. 



The phyllite is next in age, but is older than the purple series. M. 

 Hebert submits twofold evidence for this contention. (1) The purple 

 series includes beds of rounded fragments of a quartz which is iden- 

 tical with certain quartz-veins in the phyllite. One of these varieties, 

 a black quartz, is at Coutances quarried in the phyllite, and is found 

 not far off in the conglomerate of the purple group. (2) While the 

 phyllite usually dips at high angles, or is tilted to the vertical, the 

 purple series lies at much lower dips, and these relations are some- 

 times seen where the two groups are in contact. M. Hebert concludes 

 that the phyllites are Archaean ; but he would confine the term to this 

 formation, which he regards as the oldest sedimentary group, " le 

 premier terrain^ The granite and the crystalline schists are thus left 

 unclassified. The phyllite is regarded by M. Hebert as the equiva- 

 lent of the less crystalline of the Pre-Cambrian rocks of Anglesey, and 

 of the beds which, according to Prof. Green, underlie the Cambrian 

 conglomerates of Llanberis. 



The purple conglomerates and (?) shales, separated by a marked 

 discordance from the phyllite series, are placed in the Cambrian. 



It would be rash for a stranger to the district to express an opinion 

 on a question of such evident difficulty as the one before us. M. Ch. 

 Barrois, writing only last year (1885), is at variance with M. Hebert 

 on the main points discussed, and he will doubtless take up the 

 cudgels which he can wield so well. The issue, whatever it be, 

 should have an important bearing on the geology of the Channel 

 Islands, recently brought to our notice by the Rev. Edwin Hill, and it 

 may tend to smoothe, or the reverse, the troubled waters of the 

 Archaean controversy. 



It would aid our future studies in this direction if a precise meaning 

 were attached to certain terms used in M. Hebert's paper, especially 

 to the words "phyllites " (les phyllades), " schist," and " grauwacke." 



Ch. CiLLAWAT. 



laSI^OiaTS -A-ZsTID ZPiaOGIEIEIDIIsrOS. 



I.— November 17, 1886.— Prof. J. W. Judd, F.R.S., President, 

 in the Chair. — The following communications were read : — 



1. A letter from the Lieutenant-Governor of the Falkland Islands, 

 communicated by H.M. Secretary of State for the Colonies : — 



" Government House, Stanley, Falkland Islands, 

 3rd June, 1886. 

 " My Lord, — I regret to have to report that a slip of the peat- 

 bog at the back of the town of Stanley, similar to that which 

 occurred in November, 1878,' but about two hundred yards to the 

 ^ See Quart. Journ. Geol. Soc. vol. xxxv. Proc. p. 96. 



