24 P. T. C LE VE. 



part one may conclude that the geological formations are the same as in the sou- 

 thern part. 



From the want of fossils in the older rocks of S:t Martin it is not possible to decide 

 on the exact age of the S:t Martin formation, but to judge from the petrographical re- 

 semblance between the rocks of S:t Martin and S:t Bartholomew, one may conclude that 

 they belong to the same geological time. which the fossils in the latter island prove to 

 be the eocene. The general dip of the strata of S:t Martin is also southerly, as in S:t 

 Bartholomew. The small flat cay of Tintamarre near S:t Martin I have not visited but it 

 may probably prove to be a continuation of the miocene formation of Anguilla. 



SA Bartholomew, situated 62°, 51', 6" Long W. from Greenwich and 17° 53' 50" Lat. 

 (at the town of Gustavia), is a narrow island, extending east to west about 10 kilometers. 

 The whole island is mountainous and has no fresh water. Around the coasts are several 

 lagoons with brackish water. The mountains in the western part of the island form a 

 long ridge, but in the eastern part they are more isolated, conical peaks, of which some reach 

 302 — 250 meters hight above the sea-level. All the geological formations of the island 

 except the modern detrital masses in the vallies and on the plains, or recent calcarious 

 sand along the shores, belong to the elder tertiary age or the eocene time. 



The surface of the island is a very stony soil composed of rock-fragments and boul- 

 ders, sometimes of very large size, which remain to prove the strong denudation to which 

 the island has been subjected. In the places where syenite-porphyry occurs the soil is 

 covered with numerous large round boulders of this rock, which has a beautiful spheroi- 

 dal structure. 



The mountain masses of the island are composed of very different kinds of rocks. 

 One kind, the syenite-porphyr}^ is evidently eruptive, the others are partly igneo-sedimen- 

 tary breccias and conglomerates, partly fossiliferous limestone*). 



The syenite-porphyry occurs in several places as around the town of Gustavia, near 

 Grandfond, near S:t Jean, and in several other places. The rock has a greenish gray co- 

 lour, it contains small crystals of white feldspar and small black shining needles of horn- 

 blend in a greenish mäss. The rock is massive and has a flat or conchoidal cleavage. Generally 

 it has a fine concentric-spheroidal structure. By alteration the spherical boulders have become 

 very visible, and at the places, where the rock occurs, the soil is generally covered with large 

 round balls of syenite-porphyry. Sometimes it contains darker angular or rounded con- 

 cretions of a more fine-grained composition and in some few places I have found enclosed 

 in the rock smaller noduli of quartz, which does not otherwise belong to the ingredients 

 of the rock. 



In the hill behind the fort of Gustavia the porphyry is covered by a stratified fine- 

 grained claystone dipping to the north, though elsewhere the stratified rocks of S:t Bar- 



*) I was told that in the eastern part of the island is found a white fine-grained and soft limestone, employed 

 as buildingstone. I have not seen the rock on the spöt, but in the loose stones I have seen no fossils 

 remains. 



