THE ARCHIPELAGO OF CHAUSEY. 17 



they find it far preferable to any which they can 

 procure at the adjoining ports. 



The Archipelago of Chausey is essentially formed 

 of a bluish-grey granite, separated into more or 

 less extensive strata, whose regular and uniform 

 disposition is easily recognised to the south and 

 south-west of Grande-He, as well as all round En- 

 seigne. These strata, which are almost horizontal 

 in the centre of the islands, incline towards the 

 shore, and sink into the sea at an acute angle. Fis- 

 sures, perpendicular to the plane of the strata, inter- 

 secting each other at various angles, divide the rock 

 still more, and facilitate its working.* A red friable 

 stone, known in the country as rotten stone, fills these 

 interstices. Veins of pegmatite, which when de- 

 composed forms the kaolin used in the manufacture 

 of porcelain, intersect these granitic masses, which 

 are also interspersed with detached portions of quartz 



* There is a very curious circumstance connected with the work- 

 ing of the granite at Chausey which, however, is often observed in 

 other rocks of a compact structure. Before any considerable mass 

 of the stone is detached, a narrow line of about an inch in depth is 

 traced along the rock, and into this groove wedges of soft iron are 

 placed side by side. These wedges are then alternately struck with 

 a moderate degree of force, when, after a certain time, a sort of 

 musical sound is heard to proceed from the stone, which indicates 

 that it has been split through the entire mass. Nothing now remains 

 to be done but to detach the fragment which has been thus obtained. 

 When the rock is very homogeneous, the fracture is prolonged with 

 much regularity, until it meets the adjoining grooves, excepting in 

 case of its coming in contact with rotten stone. I have seen this 

 method employed to detach blocks of granite which were fully a foot 

 in thickness and more than fifty feet square, and in all cases the 

 sides of the mass were perfectly parallel and smooth. 

 VOL. I. C 



