Vol. 50.] ANNIVERSARY ADDRESS OF THE PRESIDENT. 137 



one, and at a spot on the southern cliffs of Alderney the grits may 

 be seen to rest on the crystalliue igneous mass. In estimating their 

 age, it is important to notice that they are seen to he cut by a mica- 

 trap dyke, related to the kersantons of Britanny, which Dr. Barrois 

 assigns to the close of the Carboniferous period. On the other 

 hand, they contain pebbles of the dykes which cut the granites. 

 From evidence obtained by M. Bigot on the neighbouring mainland, 

 and corroborated by the Author, it would seem that this series under- 

 lies the ' Gres Armoricain,' and may actually be Torridonian in age 

 as it seems to be in character, though Mr. Hill appears to have 

 regarded it as belonging to the Upper Cambrian of Lapworth. The 

 Jersey conglomerates were regarded as probably of the same age 

 as the Alderney grits, though the external differences are great. 

 Moreover, the presence of pebbles proceeding from the rhyolites, 

 which occupy so large an area in the eastern part of Jersey, in the 

 grits of Alderney and Omonville, is alone sufficient to show that 

 these rhyolites are not of Permian age, and cannot be placed later 

 than Cambrian times. Subsequently M. de Lapparent wrote a 

 short notice in the Quarterly Journal, withdrawing his previously 

 expressed views as to the Permian age of these porphyritic rocks or 

 rhyolites. 



The latest communication respecting the Channel Islands is the 

 joint work of Mr. Hill and Prof. Bonney, and again refers to Sark, 

 which the Authors were led to examine in the hope that its rocks 

 might afford some clue to the genesis of the hornblende-schists of 

 the Lizard. Mr. Hill's previous conclusions are summarized, and 

 amongst other matters it is stated that the planes of foliation of the 

 gneisses and hornblende-schists generally dip at moderate angles 

 and outwards from the middle part of the island. This structure 

 is said to have no connexion with faults, nor does it give any indi- 

 cation of being a result of crushing, since it has no real resemblance 

 to the pressure-structure of the Alps or of the North-west High- 

 lands ; it is, they say, a ' stratification-foliation,' not a ' cleavage- 

 foliation.' 



Three kinds of foliated rocks are described and their mutual 

 relations duly considered. Mr. Hill's Creux-Harbour gneiss, a 

 reddish biotite-gneiss, moderately foliated, but not banded, is the 

 lowest in position and apparently the oldest, though there would 

 seem to be reasons for believing that the rock is really intrusive into 

 the series which succeeds. This series is represented as consisting 

 of hornblende-schists, almost identical with those of the Lizard : 



