ORIGIN OF BASALT. ^ 279 



hasalt, wkh the matters that usually accompany them, ochres, Facts and ob- 



xeolites, chalcedonies, and calcareous spar; while at iEtna and servations re- 

 ,, . , ., , 1 specting basalt 



V esuvius he met wjth burnt matters alone, in the county 



The points of view in which I shall compare volcanic coun- of Antrim; ad- 

 Iries, as described by the most accredited writers, with our jh^^ ^^ jg j^ot 

 basaltic district, so often referred to by the same authors, volcanic. 

 are: 



First. The prominent features and general resemblance. 



Secondly. The different arrangement of the materials in vol- 

 canic, and our basaltic countries. , 



Thirdly. Frequent change in the arrangement ol the ma- 

 terials in our basaltic country. 



Fourthly. Striking and radical differences between our 

 basalt strata, and all known currents of lava, 

 i- Fifthly. Substances found imbedded in our basalt, and 

 never in lava. 



Sixthly. Different effects produced upon ibreign sub- > 

 stances (particularly calcareous), when coming in contact with 

 basalt and with lava. 



Seventhly. Divisibility of the mass into regular forms, essen- 

 tial to basalt, but never noticed in lava. 



First. The general and leading features of volcanic coun_ 

 tries are admitted to be isolated mountains, generally conic, 

 truncatiid cones, vast craters, with currents of lava issuing from 

 them, which may be traced many miles. But as all writers 

 upon this topic candidly admit that we have nothing similar in 

 this country, I will not press the argument, nor enquire whe- 

 ther their modes of accounting for the want of these features 

 be satisfactory or not. 



Secondly. If basalt be lava, and (as this theory supposes) 

 once flowed from a volcano, we should expect to find it ar- 

 ranged in the same manner with the currents of lava, which 

 are contiguous to most known volcanos. But here the diffe- 

 rence is most striking: for, while all writers that describe 

 \Glcanic countries, represent the ejected matters as confusedly 

 arranged, and altogether a heap of disorder; with us we 

 observe, in the dispo al of our basalt, the most consummate 

 regularity ; every separate stratum preserving steadily its own 

 place, and never breaking into that of another. 



Besides, most writers admit that currents of lava are fiever 

 parallel to one another : while our basalt strata, accu- 

 mulated 



