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Dr. Nugent on the Geology of Antigua. 141 
Memorandum concerning the Geology of Antigua, §c. 
Tux southern and more mountainous part of the island con- 
sists of trap rocks; more particularly of trap breccia and 
wacké porphyry. On these beds rests a series of very pecul- 
‘jar stratified conglomerate rocks. ‘These strata vary exceed- 
ingly in colour and thickness, but all dip, at a considerable an- 
gle, 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 gritnerde,* (or chlorite Baldogée.) ‘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 it is owing 
to manganese and iron. ‘The conglomerate character of this 
rock is derived from its having imbedded in it, or incorporated 
with it, numerous fragments, of ail sizes, of petrified wood, 
chert, with and without coralline impressions, agate, jasper, 
amygdaloid, greenstone, hornstone, porphyry, porphyry-slate, 
and other substances. 
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 
itis 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 3 though at the Chorch-hill, at St. Johns, formed 
of this chert, casts of bivalve and ramose madrepores, are like- 
wise found. The calcareous beds are principally of 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 
18 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 green earth of most mineralogists.+-Ecilor. 
t Formation—a geological phrase, of German origin. 
