Geological Survey of the Island of Jersey. 369 



I have observed five varieties. 



Argillaceous pebbles! 



Sienitic do. [» in an argillaceous matrix. 



Porphyritic do. J 



Argillaceous do.* 1 {n a s ; enitic matrk 



Sienitic do. J 



6, 9 and 9 a, are illustrative of most of these when freshly 

 cut : the argillaceous varieties of this rock are hard enough ; 

 but they all fail exceedingly on exposure to the weather, the 

 matrix more perishable than the clay-pebbles it contains, which, 

 however, betray their origin, by shaling and splitting after a 

 short time. These last, as well as the sienite-pebbles, some- 

 times weigh several hundred weight, and are as thoroughly 

 rounded as the small ones. 



Sulphuret of iron and manganese still maintain their ground, 

 the latter enveloping the pebbles with a thin film, and with the 

 former penetrating the matrices (6), although I heard the 

 best character, for quantity and quality, of the water of this 

 rock. 



Diluvium, or Sea Beach? 



The rocks on the shore, from Rozel Harbour to Gouray at 

 Le Hoc, under Fort Regent, from thence to the second Mar- 

 tello Tower in St. Aubin's Bay, from Blanc Pignon to L,a Car- 

 riere, and at L'Estac, emerge from the diluvial deposits lying 

 at the bottoms of the vallies and round the bases of the 

 sea-side hills, forming abrupt banks from 20 to 50 feet high, 

 and invariably composed of the debris of the nearest rocks 

 respectively. 



The lower strata of these banks often consist of well-rounded 

 pebbles : this fact is well-exemplified at the little bay a, at 

 L'Etac, where the superincumbent debris is at least 50 feet 

 high, and is a thorough mixture of the two rocks, which come 

 into contact at this spot. 



The hills are capped in general with a sandy clay (55) inter- 

 mixed with debris of the contiguous hills. 



The flat ground at the mouth of St. Peter's Valley is a com- 

 plete morass, so that 1 could obtain no information respecting 

 it; but from what I have observed at St. Aubin's Pier, as com- 



