SAEK, HEK3I, A2TD JTIHOr. 



331 



contact at leisure. The dip here is 15° or 20° X.~\V., and here also 

 the massive rock makes a close approach to conformity, but on a 

 small scale seems to cut across or run into the bedding ; so that 

 again in Brecqhou we have the same imperfect indications which 

 just fall short of proof. 



Yet the general conclusion from the junction-evidence, taken as a 

 whole, even if we leave out that of the south-east junction, must, I 

 think, be that these upper crystalline masses are not sedimentary rocks 

 metamorphosed, but one igneous overflow. The near conformity in 

 each case may be due to the granite having forced itself between 

 beds as a direction of least resistance. But it seems to me also 

 possible that an actual flow may have taken place over a surface 

 nearly horizontal, and that the coarsely crystalline nature may be 

 due to a higher temperature or other unknown circumstance of that 

 prodigiously remote epoch. In either case denudation has had a 

 protracted task to plane down through the superincumbent 

 mass and lay bare the subjacent dome. There are difficulties, but 

 they seem less than the difficulty of accounting for the invariable 

 appearances of flow across the edge of beds, the apparent intrusive 

 offshoots, and the sudden transition from a minutely banded series 

 to a mass a thousand feet thick, with only phantoms of bedding 

 which flee upon approach. 



The overlying rocks in Brecqhou present remarkable features. 

 At the furthest western point of the island they slope gently down 

 to the sea, and show no greater differences from those at the ex- 

 tremities of Sark than rather more mica and somewhat greater 

 decay. But along the southern cliffs, approaching the deep inlet con- 

 spicuous on the map, a structure begins to be extremely well marked 

 and weathers out into deep furrows. The clean faces of hand- 

 specimens show a banded arrangement of constituents such as is 

 usually regarded as characteristic of a fine-grained gneiss. The 

 dark materials gleam with mica, the white streaks are coarser and 

 consist of felspar with some quartz. So far as I could see, the 

 passage from the crystalline rock to this is gradual and continuous, 

 so that the whole mass is one. I have unfortunatelv made onlv 

 one examination of the spot : a boat has to be taken, and it is not 

 always possible to land. 



This gneissoid structure affords no valid argument in support of a 

 metamorphic origin for the crystall in e rock. If it should be proved 

 separate, it would of course prove nothing one way or other. If, as 

 I believe, it is continuous with that, then, since it is clearly a lower 

 part, almost in contact with the schists, we should have to admit 

 that metamorphism had been much less complete in the deepest- 

 seated portion of the mass. 



The banding shows corrugations visible even in hand-specimens, 

 and becoming "contortions of some magnitude towards the head of the 

 deep inlet on the south coast. They lie X.-S., and are plain proofs 

 of an E.-TV. crush or nip, of which other indications exist. It 

 would appear that this great squeeze produced more visible effects 

 where the granite (assuming that this gneiss is crushed granite) 



