FLORA OF ST. CROIX AND THE VIRGIN ISLANDS. O 



the island, reaching in some places as high as 1150' (Mount Eagle), l3ut 

 averaging 600'-800' only. 



The rock of these hills is nearly the same as in the above-named 

 group, although the Bluebit of this latter occurs more rarely, and is sub- 

 stituted by a fine, greyish, stratified clay-slate, without vestiges of any 

 organic remains. The strata of this slate are often very much disturbed, 

 so as to present an exceedingly broken and overturned appearance. The 

 greater, western part of the island forms a large, slightly inclined plain, 

 sloping towards the south, and interruiited in a few x)laces by low, short, 

 isolated ridges only 200'-300' high, and formed of a tertiary lime- 

 stone of the miocene period. This limestone is covered by a layer of 

 detritus and marls some feet thick, but shows itself at the surface in 

 various places, and contains several fossils, partly of still existing species 

 of moUusca. 



Along the coasts are found some new alluvial formations, often enclos- 

 ing lagoons, some of which are of considerable size. These lagoons are 

 being gradually filled up by vegetable matter, as well as by sand and 

 stones washed down by the rains from the hills ; but whilst in the Virgin 

 Islands many similar lagoons have been raised already several feet above 

 the level of the sea, and laid completely dry, no such thing has been 

 observed in St. Croix. This seems to indicate that no rising of the ground 

 is taking place in the latter, as is the case in the former, as mentioned 

 above. From its whole structure and formation it may be inferred that 

 the soil is more fertile in St. Croix than in most of the Virgin Islands, 

 Vieques excepted, the sugar-cane being cultivated to a considerable ex- 

 tent on the island. 



Whilst thus the geology of St. Croix and the Virgin Islands presents 

 some not unimportant difl^'erences, the climate may, on account of their 

 similar geographical position, as well as elevation above the sea-level, be 

 said to be materially the same in both. 



In accordance with the geograj)hical position of the islands, the tempera- 

 ture is very constant and high, the yearly mean average being 27.2° C, 

 divided nearly equally over all the months, the coldest, February, show- 

 ing 25.6°, the warmest, September, 28.9°, a difference of 3.3° only. The 

 same uniformity is observed in the daily variation, which scarcely ever 

 surpasses 5°, the thermometer rising gradually from 6 a. m. till 2 p. m., 

 and falling just as gradually during the rest of the 24 hours. 



Thus the difference of temperature at the various seasons of the year 

 is too small to affect the life of vegetation to any very perceptible ex 



