Dr. JVvgent on the Geology of Antigua. 141 



Memorandum concerning the Geology of Antigua, 4*c. 



The southern and more mountainous part of the island con- 

 sists of trap rocks ; more particularly of trap breccia and 

 wacke-porphyry. On these beds rests a series of very pecu- 

 liar stratified conglomerate rocks. These strata vary exceed- 

 ingly in colour and thickness, but all dip, at a considerable 

 angle, to the northwest. The more usual character of this 

 rock, is that of a clayey basis, with minute particles of felspar, and 

 small spots of griinerde* (or chlorite Baldogee.) This latter is 

 frequently diffused over the whole, and gives it a green tinge : 

 the colour has been thought by some to proceed from the im- 

 pregnation of copper, but I am rather of opinion that is owing to 

 manganese and iron. The conglomerate charficter of this rock, is 

 derived from its having imbedded in it, or incorporated with 

 it, numerous fragments, of all sizes, of petrified wood, chert, 

 with and without coralline impressions, agate, jasper, amygda- 

 loid, greenstone, hornstone, porphyry, porphyry slate, and 

 other substances. 



On this singular class of strata, reposes an extensive calca- 

 reous formation, occupying the northern and eastern part of 

 the island, having subordinate to it, and at its lowest part, where 

 it is in contact with the conglomerate, large beds and patches 

 of chert, which contains also a vast variety of petrified woods, 

 several of which are of the palm tribe , with silicified shells, 

 chiefly cerithea ; though at the Church-hill, at St. Johns, formed 

 of this chert, casts of bivalve and ramose madrepores are like- 

 wise found. The calcareous beds are principally of a friable 

 marl, with blocks and layers of limestone irregularly included. 

 In this formation] are many fossil shells, both in the calcareous 

 and siliceous state ; and there appear to be some beds, wherein 

 is a mixture of shells of marine, and others of a fresh water, 

 or at least a terrestrial origin. The coralline agates found in 

 nodules and patches therein, and which may readily be dis- 



* The greea earth of inost mineralogists. Editor. 

 f Formation — a geological phra:-e, oi' Germaii origin. 



