NOME I. D. BASALTIN. 237 



" 305. Amygdaloid resembling basalt, in which 

 small groups of zeolite occur, which in some 

 places have totally lost their water of crystallisa- 

 tion. 



" 306. Similar amygdaloid, out of which all 

 the extraneous parts have decayed, therefore the 

 whole has a perfectly porous appearance ; from 

 Ascherofen, in the Thuringian forest. 



" 307. A piece of amygdaloid in which not 

 only all the extraneous parts have decayed out, 

 but the basis itself is also very much decayed ; 

 hence such varieties are not unfrequently called 

 pumice ; from Upper Lusatia." 



As the opinion concerning the volcanic nature 

 of basaltin seems rather to gain ground, it is not 

 improbable that some of those substances are 

 truly volcanic. When we consider the vast num- 

 ber of volcanoes in Asia and America, amounting 

 to about one hundred and fifty, we may very rea- 

 sonably infer that many in Europe may have be- 

 come extinct. As these appearances only affect 

 small spots, prejudice on either side becomes truly 

 ludicrous ; and its excess will, with rational minds, 

 turn the scale upon. the other side. What shall 

 be said, when a late writer has informed us, that 

 pumice itself is commonly a Neptunian sub- 

 stance ? 



