16 P. T. OLEVE. 



The sea between S:t Croix and the Virgin-Islands is very deep, about four thousand meters 

 according to soundings taken by R. Hamilton*). 



The island has some smaller rivulets, the most important is Salt River in the nor- 

 thern part. 



The geological formations of the island belong to different ages. The northern 

 mountain ridge is the oldest, and to judge from its great petrographical resemblance with 

 the rocks of the Virgin-Islands it would seem to belong to the same geological age as 

 the latter, or the cretaceous. Upon those highly disturbed strata very little disturbed 

 beds of coralline limestone and white marls rest; they are probably of the miocene age. 

 The youngest formation consists of detritus swept down from the mountains by rains and 

 mixed with the white marls, and in a recent formation of calcarious sand around the shores. 

 The oldest formation is composed of different kinds of rocks, igneous or igneo-sedimentary, 

 as diabase, diorite, bluebeache-conglomerate and felsite. or sedimentary stratified rocks as 

 clay-slate and limestone. 



The igneous or igneo-sedimentary rocks are very difficult to describe, the surface 

 of the mountain often being very much altered and covered with shrubs or detritus. Still 

 the resemblance of the rocks in the mountains west of Christianstced to the bluebeache- 

 conglomerate of the Virgin-Islands seems to be very great. Around Christianstced the pre- 

 ponderating rock is felsitic. The felsite is here a compact, harel rock, commonly breaking 

 in angular pieces. It has a white, yellowish or greenish colour, and contains some small 

 black crystals of hornblend. In the vicinity of Christianstaed and in the town the rock 

 has a distinct variolitic strueture, easily visible when the surface has been exposed some 

 time to the air. It seems then to be composed of balls of the size of a pea densely im- 

 bedded in a soft mäss. The rock has some indication of a stratified strueture; in Chri- 

 stianstaed the strata strike E. N. E. — W. S. W. and dip S. S. E. Near Beeston Hill 

 their strike is N. N. W. — S. S. E. and dip W. S. W. at about 50°. In the latter place 

 the rock is irregularly broken into angular pieces by fissures at right angles to the sur- 

 face of stratification. Near the harbour of Christianstaed I have seen felsite alternating 

 with black, somewhat silicified, clay-slate in regular strata from E — W., dipping southward 

 at about 45°. The felsite is easily altered and transformed to a loose stone called by the 

 inhabitants »rotten-stone». The old Caribbean savages have employed the felsite for ma- 

 king their iinpleinents. Diabase occurs in some places in dikes penetrating the older rocks 

 as the clay-slate near Christianstaed and at La Vallée. Near estate Lebanon Hill are many 

 loose round boulders scattered on the ground. They seem to be diabase, but I have not 

 seen the rock »in situ». Diorite also occurs in the island as near South-gate, where it is a 

 granular, whitish mixture of white feldspar and greenish-black hornblend. Loose blocks 

 of the same rock are scattered över the plain south of South-gate. In the small Green- 

 Cay there is a remarkable variety of diorite with enormous masses of white feldspar, 

 inixed with some quartz and large crystals of black hornblend. The rock contains some 

 epidote and granules of pyrite. Almost the whole eastern part of S:t Croix is occupied 

 by steep and picturesque mountains of clay-slate, of which, also, the hills north and north 



*) Kindly ooramunicated by the Governor of the island M. Berch. 



