84 P7^of, Liveing, On the metamorphism, of rochs, dc. [Oct. 29, 



lumps, while the felspar forms larger crystals. So in the por- 

 phyritic part, where the imbedded crystals of felspar are large, 

 so are also the lumps of quartz. A good deal of Jersey is made up 

 of shales and slates, but these are unconformable with the syenite. 

 At Letacq, the northern extremity of St Owen's Bay, the syenite 

 cuts through the shales right across the bedding. The shale at the 

 junction is very hard and full of joints, and in some places has the 

 stratification obliterated, and one might fancy that it had been 

 altered by heat; but I found the shale in precisely the same con- 

 dition elsewhere, where there was no syenite near to it; and more- 

 over the shale is not altered all along the junction with the 

 syenite, in places it is quite unaltered and adheres very closely 

 to the syenite. The crack between the syenite and shale has been 

 the condition determining metamorphosis so far as it has occurred. 

 The shales vary in character in different parts of the island to a 

 wonderful degree. At one place, La Crete point, a little north of 

 Gorey, they pass into a sort of hornstone with a regular columnar 

 jointing. Ansted calls attention to this spot. The stratification 

 of the rock at this point is quite distinctly seen as a striping of the 

 compact mass, and sometimes as regular layers of minute bubbles. 

 The rock looks to me as if it had really been almost fused, and 

 had acquired its columnar jointing, not a crystalline texture, in 

 cooling. 



I was unable to explore the whole island. Ansted remarks 

 upon some conglomerates which I had no opportunity of exam- 

 ining-; but I came across one which I think he does not mention. 

 It forms part of the projecting headland at Plemont on the north- 

 west of the island. It is stratified, and consists of rounded pebbles 

 of all sizes from an inch to a yard in diameter. Most of these 

 pebbles are of the syenite of the neighbourhood, but there are 

 besides a good many pebbles of other rocks, many of a micaceous 

 rock which I have not seen elsewhere in the island. The curious 

 point about this conglomerate is that the matrix is granitic. It is 

 in a somewhat rotten condition as if weathered, but still hard 

 enough to stand much pounding by the sea, and under the hammer 

 both matrix and pebbles break through together. The weathering 

 of this matrix is quite of a peculiar character, the ordinary syenite 

 separated by joints merely weathers away at the angles, but this 

 granite weathers in channels and pits, taking fantastic forms like 

 weathered limestone. It must be a re-made granite, but though 

 the pebbles are arranged in strata it is plain that the materials 

 of the matrix have not been assorted by water, for they are mixed 

 quite as in ordinary granite. I believe the deposit to be an old 

 sea beach which has been raised and then the pebbles have 

 crumbled under the action of the weather, the crumbled parts 

 have filled up the interstices and afterwards the whole has been 



