Geological Survey of the Island of Jersey. 365 



this island, although it is found at Guernsey. Hitherto I have 

 been unsuccessful in obtaining it in situ ; but, from the large 

 masses near Vicart and at Boulay Bay, the parent rock can be 

 at no great distance. 



These large masses are agglomerates of the same bodies, 

 only they are about the size and shape of potatoes of various 

 dimensions, standing out in full relief, of the colour of 12, 

 which appears to be only a variety of this rock, the chief dif- 

 ference being the regularity of the concretions ; which last cir- 

 cumstance, I have however found in every degree, assuming 

 Nos. 4 and 12 as extremes. It is used in the construction of 

 piers, and in cases where large blocks can be best turned to 

 account. 



5. Apparently a white variety of No. 2, which it underlies, 

 and of which it contains small portions. The concretions shew 

 evident symptoms of 5, a. 



Epidote, serpentine, and diallage are found in small quanti- 

 ties at Boulay Bay. At the mouth of the Trinity Valley, the 

 bed of the stream contains small rounded pebbles, covered 

 with a coat of the black oxide of manganese, nearly one- 

 fortieth of an inch thick. 



Felspar and Quartz. 

 43. — From the neighbourhood of Noirmont and Le Corbiere, 

 where it is to be found in plenty. 



Felspar and Hornblende. 

 15 is from La Motte, and not very abundant ; it is taken 

 from among 16 and 17 rocks j 18 and 19 are specimens of the 

 whole coast of sienite, at the south-east of the island, begin- 

 ning at Fort Regent, and reaching to Roque Berd ; also from 

 Sorel to the bay marked x, at the north of the island. This 

 variety always assumes a reddish aspect (from the oxide of 

 iron in the hornblende) at the surface ; and the crust thus 

 formed can be generally detached by a light and sharp blow. 

 From the frequent inequality of disposition of the hornblende, 

 this rock bears often a singularly mottled appearance, as at 

 Elizabeth Castle, where the rock 38 may be well taken for a 

 conglomerate, until this habit is known. Another example of 

 this is given in 52. At the south-west point of the Hermit 



2 B 2 



