1817.] GEOLOGY OF THE WEST INDIES. 137 



ance of transition formation; several species of horn- 

 blend rock, a little crystalline; amigdaloid, containing 

 small nodules of calcaire and zeolite, or almonds, which, 

 when the stone is fresh broken, are undistinguishable from 

 the mass, and discover their difference only when in a state 

 of decomposition; a soft argillaceous mass, with spots 

 of green, resembling the green earth of Verona; porphyry, 

 with crystals of quartz and feldspar, imbedded in a red 

 argillaceous base, &c. all of them alternating one with ano- 

 ther, occasionally, and assuming the appearance of a tran- 

 sition formation. But the various aspects which these 

 rocks present, and the different stages of decomposition in 

 which they are found, and in which they differ much from 

 the rocks of a continent, or of northern climates, render it 

 extremely difficult to determine which part may be secon- 

 darv, and which transition. 



St* Martin and Anguilla are two small stratified 

 islands, on a line with St. Bartholomew, and consisting of 

 a similar formation. 



The island of St. Thomas may also be classed in this 

 range. It is stratified, though in much confusion, and so 

 deranged as to render it difficult to ascertain the general 

 direction, which appears to be from north-west to south- 

 east, dipping easterly. The rocks consist of a variety of 

 agregates, resembling the transition, some of which when 

 fresh have the appearance of hornblend rocks, but when 

 beginning to decompose, the agregate appears, with a few 

 plates of a black crystalline rock like hornblend. I found 

 a yellowish brown quartzy agregate, resembling a rock, in 

 the transition, at the Lehigh Falls in Pennsylvania. 



Santa Cruz. This island, though included in our first 

 division, agrees rather with the direction of the volcanic 



