ON THE GEOLOGY OF THE NORTH-EASTKRK WE8T-INDJA ISLANDS. 7 



of beautiful, härd and crystaline limestone or marble, of a bluish-gray colour and parallelo- 

 pipedic structure. 



S:t Thomas. Thacht Cay. - Hans Lollik. Grass Cay. 



The sketch is taken from S:t John. 



Hans Lollik. North of S:t Thomas are two smaller Islands called Hans Lollik. The 

 rock is a härd and compact dark green diabase with crystals of augite and sometimes 

 impregnated with magnetic pyrite. No trace of stratification is visible, but the structure 

 of the rock is distinctly parallelopipedic. 



West of Hans Lollik are two smaller islets Inside Brås and Outside Brås. Neither 

 of them was visited by me, but. I have sailed very close by them. The former islet seems 

 to be composed of bluebeache rock; in the latter stratified rocks occur, striking E — W 

 and dipping at an angle of 70° to the north. I have not landed at the small islets N. W. 

 of S:t Thomas, the Cockroach Islands and Dutch-man Cape, but I have passed very near 

 Salt Cay and West Cay, which are probably bluebeache-rocks. 



3. Culebra or Passage Island is a Spanish possession about 20 kilometres from S:t 

 Thomas. The island is uninhabited and covered with a thick vegetation of prickly shrubs, 

 cacti, etc, almost iinpossible to penetrate. The island is not very high, being only 198 

 metres above the sea, and, to judge from the rocks on different parts of the coast, entirely 

 composed of a dark-gray or brown labrador-porphyry. I have seen a darkgreen trsp- 

 like rock only on the small island of Culebrita. The labrador-porphyry has a fine sphe- 

 roidal polygonal structure, so that the seacliffs look as if they were constructed of large 

 polygonal boulders. The rock is traversed by numerous veins, containing white quartz 

 and often beautiful transparent rock-crystals. Sometimes the veins are filled with cal- 

 carious spar and epidote, or a green or red quartz, or iron-silex. 



4. S:t John, situated at a short distance from S:t Thomas, is, like the other Virgin- 

 Islands, rnost extended from east to west, or about 15 kilometres. Its greatest breadth 

 is about 7 kilometres. The south-eastern point of S:t John forms a triangulär promon- 

 tory, and the north-eastern a long, narrow head-land, between which lies the large and 

 beautiful Coral Bay. On the northern coast there is a promontory called Marys Point, 

 which is connected with the island by a low and narrow isthmus. The whole island is 

 mountninous and consists of branching ridges, separated by narrow and deep vallies of 

 delightful beauty. The highest point is the Camel Peak in the centre of the island. It 

 reaches an elevation of 373 metres above the sea and Bordeaux Peak near the middle of 

 the western coast is almost equal in hight. Permanent springs are rare, as are also la- 

 goons near the shores, as the rocks commonly dip down abruptly into the sea. The geo- 

 logy of the island bears a great resemblance to that of S:t Thomas, of which S:t John is 

 a continuation. The middle part of the land consists of the same green conglomerate as 

 in S:t Thomas; the southern bilis with their shining red sea-cliffs are composed of felsitic 

 rock, and in the northern part stratified metamorphic rocks are visible. 



