ROCKS OF THE CHANNEL ISLANDS. 31 



seeing a full account of the structure of north-western France 

 as at present known, but Rev. E. Hill, F.G.S., has recently 

 read before the Geological Society of England, various papers 

 on the Channel Islands, in which he refers to the correspond- 

 ing rocks in France, and mainly on the strength of these and 

 of a treatise on the " Geology of Jersey," by M. Noury, which 

 shows a careful examination of the structure of that island. 

 I have ventured to put together a few remarks on the subject 

 I have chosen for this paper. My conclusions in the main 

 agree with those of Rev. Hill, but my point of view may be 

 somewhat different. 



Jersey contains by far the largest variety of rocks, which 

 are evidently of various ages, and although their ages cannot 

 be absolutely fixed, their relation to each other may at least 

 be ascertained, so that this island may serve as a standard 

 with which the others can be compared. The oldest rocks in 

 the islands have, I consider, been proved to belong to the 

 Archaean period. The term " Archaean " was introduced by 

 Dana, an American geologist, in 1874, and is now generally 

 applied to rocks older than the Cambrian formation in which 

 sense it is synonymous with the term " Pre-Cambrian " also 

 often used. These terms, however, must not be considered 

 synonymous or co-extensive with " Metamorphic," as all 

 Metamorphic rocks are not necessarily Archaean, nor all 

 Archaean rocks Metamorphic. The Archaean period, it is 

 evident from its definition, must include an enormous lapse 

 of time, exceeding perhaps all the other periods put together. 

 The greater part of the rocks in the Channel Islands belong to 

 the Archaean formation, although Jersey has but a small area 

 of them. To begin, however, with that island, a considerable 

 portion of the reefs of rock known as "Banc du Violet," 

 consists of diorite which is seen to be penetrated by masses 

 and veins of red granite clearly of later date. Other patches 

 of diorite are found at Grouville and near Sorel (St. John's), 

 also penetrated in the same manner by the granite. No 

 gneiss occurs, although a slight trace of gneissic structure in 

 the rocks near St. Clement's is noticed by M. Noury. Near 

 Yicard Harbour is found a rock to which M. Noury directs 

 attention as being first noticed by him, and which he styles 

 " Chloritoschiste." It is bordered by the quartz felsites or 

 rhyolites which blend with it to a certain extent. I think 

 this Chloritoschiste is also Archaean. The diorite above 

 referred to does not penetrate other rocks, and therefore 

 appears to be the oldest rock in Jersey. There is, however, 

 at Anne Port, a vein of diorite intrusive in quartz felsite, and 



