and the other Channel Islands. 7 



undimmished force of the wind and the sea, it has undergone consi- 

 derable changes, and many detached rocks of rude forms are the 

 consequence. And on this side it is in many places so thoroughly 

 decomposed, as to have formed a white, powdery, siliceous soil, much 

 resembling tripoli. 



The whole of this porphyry has a hornstone basis, and is either 

 red, grey, or white. Together with the felspar, it frequently contains 

 imbedded grains of quartz. On the beach 1 picked up flints, and 

 pebbles of different coloured hornstone. It is a necessary conse- 

 quence of such an arrangement of rocks, that a great part of the soil 

 of Alderney should be sandy. It is nevertheless well supplied with 

 water, and produces good crops of grain and vegetables. Its valuable 

 breed of cows is well known. 



The precipitous rock Ortac lies a mile and a half to the westward 

 of Alderney. It is about an hundred feet high, and connected with a 

 chain of rocks that stretches from Burhou. And at the distance of 

 seven miles in the same direction are the Casquets, remarkable for 

 their well-known lighthouse, and consisting of many high and sunken 

 rocks. I had no opportunity of visiting any of these, but was 

 informed that they consisted of the same grit as the eastern end of 

 Alderney. The figure of Ortac would however lead me to think 

 that it was formed of porphyry, as its precipitous appearance is not 

 so consistent with the tendency of the grit I have described. No 

 organic remains have, as far as I know, been found in Alderney. 



GUERNSEY. 



The approach to Guernsey is also full of danger, from the number 

 of the rocks, and the rapidity of the tides which surround it. 



