-I. he following pages contain some of the scientific resulta of a geological voyage in the 

 northeastern West-Indian Archipelago, which I made in tlie winter 1868 — 69. I expected 

 that this part of the West-Indies would offer the greatest geological variety, as two dif- 

 ferent lines of elevation cross each other there. For this reason I visited first the Virgin 

 Islands, and proceeded afterwards to S:t Bartholomew and the surrounding islands of An- 

 guilla, S:t Martin, Saba, S:t Eustatius and S:t Kitts. In Puerto Rico I had hopes of mee- 

 ting united the different geological formations, that I had studied in the smaller islands, 

 and I had a great wish to explore that large and beautiful island, but the short time, I 

 was able to stay in the West-Indies, and the inany difhculties in the .geological study of 

 a large and mountainous tropical island without any good topographical map, did not 

 allow me to get more than a very incomplete acquaintance of the geological structure of 

 this island. 



As I have not yet had time for a careful study of iny collections of fossils, I re- 

 serve the paleontology for a future cominunication and here treat only of the geology, the 

 mineralogy, and the petrography of the West-India islands. 



All the measures of the hight of the mountains or the extent and situation of the 

 islands, given in this treatise, are taken from the rnaps published by Messrs Laurence, 

 Parson and Barnett as well as from some Danish Maps. 



I have added to my own observations a short summary of the geology of the other 

 parts of the West-Indies, as far as it is known from publications. 



I. Virgin— Islands. 



The group of islands east of Puerto Rico is called the Virgin Islands; they have a 

 general direction from west to east. The largest among them are Culebra, Crab Island, 

 S:t Thomas, S:t John, Tortola, Virgin Gorda and Anegada. Beside those larger islands are 

 more than fifty smaller islets or cays. The sea between the islands and Puerto Rico is 

 generally only 30 — 50 metres deep, but at a short distance north and south of the archi- 

 pelago the bottom is not reached for several hundred metres. The islands may conse- 

 quently be regarded as the summits of a submarine chain of mountains, continued to the 



