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Geology of Antigua. 85 
fectly agatized, that they are cut by lapidaries for jewelry and 
other ornamental purposes. In addition to these, nodules of chert 
are found in the clay formation, detached from the beds of chert ; 
and also agate nodules, of which I have before spoken. I do not 
see how either of these classes of fossils and minerals can be re- 
ferred to silicious springs; for there is no evidence that such 
springs have existed where they are found, or that they could, 
under any circumstances, have been produced by them. I am 
tia that Lyell and some other geologists have ascribed analo- 
ous phenomena fo heated vapors and aqueous solutions charged 
vith silex, and forced up through the superficial strata from the 
interior of the earth. To say nothing of the adequacy or inade- 
guacy of such a cause to produce the phenomena in question, I 
think a person who has well considered the concretions with 
which many clay beds abound—the nodules of flint in chalk— 
the segregation of mineral matter from the mass with which it 
must have been originally blended, and its aggregation into dis- 
tinct crystalline forms—and, also, the contents of metalliferous 
veins and fossil fissures of rocks, must have recognized an agency 
better adapted to the present case, than any sublimation from the 
interior of the earth. Mr. Bird’s suggestion, at the last meeting 
of the British. Association for the Advancement of Science, that 
wood is silicified by electrical influence, is certainly countenanced 
. by many facts; and it is to be hoped, that the experiments which 
he has commenced on the subject, together with those on the 
formation of minerals, will do something towards defining an- 
other boundary of the immense but mysterious domain of elec- 
trical agency. — It is possible that all the petrifactions of which I 
have-spoken in Antigua, mays at length be referred to this source. I 
see nothing in their chi which forbids such 
a supposition ; but, in the. present state of our knowledge, I think 
the explanation which I have given is the most probable. I am 
aware, however, that these fossils and the whole geology of the 
island need a much more minute examination than they have yet 
received, in order to draw any theoretical conclusions, in which 
entire confidence can be placed. I know of no field which would 
“more amply repay the geologist for such an examination ; and 
should the imperfect sketch which I have given, have no othe? 
effect than to direct the attention of some one to this island, J 
Song not consider myself to have hi in vain. 2 
3 
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