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 

 aware, that Lyell and some other geologists have ascribed analo- 

 gous phenomena to heated vapors and aqueous solutions charged 

 with silex, and forced up through the superficial strata from the 

 interior of the earth. To say nothing of the adequacy or inade- 

 quacy 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, may at length be referred to this source. I 

 see nothing in their character or circumstances 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 other 

 effect than to direct the attention of some one to this island, I 

 shall not consider myself to have labored in vain. 



