2 FLORA OF ST. CROIX AND THE VIRGIN ISLANDS. 



bold and rocky, forming abrupt promontories of considerable hciglit 

 and pictnresqne appearance, the hills and ridges on tlie otber band 

 being more rounded and of a softer outline. 



Tbe whole group of islands, with the exception of Anegada, which is 

 built up of a tertiary limestone of very recent and probably pliocene 

 date, belongs to the cretaceous period,*showing as the principal rock a 

 breccia of felsite and scoriaceous stones, the cementing i^art of which 

 probably consists of decomposed hornblende, and having its cavities 

 commonlj' filled with quartz or calcareous spar. Besides this principal 

 rock, which is often found distinctly stratified, and which is called 

 Bluebit by the inhabitants, who generally employ the stone for building 

 materials, limestone, diorite, clay-slate, and other less frequent minerals 

 also occur in the islands, forming, however, only a poor substratum for 

 vegetation everywhere. For the product of the decomposed rock is 

 generally a red heavy clay. Only Vieques shows a more fertile soil, pro- 

 duced by the alteration of a syenite-like diorite, its more level surface at 

 the same time allowing the fertile strata to remain on the surface; whilst 

 in the other islands the heavy rains as a rule will wash the loose cover- 

 ing of the ground down to the sea. 



From various facts observed in Anegada and Virgin Gorda by Sir R. 

 Schomburgk,f as well as by Mr. Scott, in Vieques, at Porto Ferro Bay, 

 it appears that at the present period the whole chain of islands is slowly 

 rising, so that perhaps in a geologically speaking not very distant time 

 most of the islands may become connected reciprocally and with Porto 

 Eico. 



To the south of the Virgin Islands, at a distance of about 32 miles, and 

 between 17° 40' and 17^ 47' N. lat., 64° 35' and C4o 54' W. long., lies the 

 island of St. Croix, geographically considered an outlying part of the 

 former groui>, but separated from it by an immense chjism of more than 

 2000 fathoms, as stated above. This extraordinary crevice has no doubt 

 been formed at an early period, and has in various respects contributed 

 materially to isolating the island from its neighbours. 



St. Croix is of about 57 square miles, and has a triangular form, with the 



greatest length, some 20 miles, from east to west, the greatest breadth 



being about 5 miles, in the western i)art of the island, which becomes 



gradually narrower towards the east. The coast-line is more connected 



and the surface more level than in most of the Virgin Islands, the hills 



stretching only along the northern coast and through the eastern i^art of 



*Clevc: On the Geology of the North-eastern West India Islands. Stockholm, 1871. 

 tBerghaus: Almaoiacb llir das J^^ahr 1837, pp. 405 and 408. 



