314 DOMAIN XII. VOLCANIC. 



ancients; whose most common admixtures are 

 quartz and felspar, and in some porphyries 

 chalcedony. This observation, if exact, would 

 seem of itself to indicate a different origin ; for 

 if basaltin were merely the more earthy and 

 compact appearance of the siderous substances, 

 hornblende, and grunstein, as asserted by the 

 Wernerians, it seems difficult to imagine why its 

 parasites should thus totally differ. Chrysolite 

 or olivine also occurs in the masses of native 

 iron, and other stones said to have fallen from 

 the atmosphere; and which are well known to 

 appear in the form of fiery meteors, and to bear 

 other palpable marks of fusion by heat*. 

 Arrangement. In this division, the terms HYPONOME and 

 MICRONOME, implying greater and smaller sub- 

 divisions of the Nome, will become still more 

 necessary, and more strictly applicable, as,, 

 though the subjects resemble each other, they 

 are widely different in a geological point of 

 view. The want of such denominations has 

 obliged the writers on volcanic products to di- 

 vide them into new and unusual classes, genera, 

 and species ; in, violation of the other provinces 

 of mineralogy, where these terms bear quite a 



* Perhaps in a heated state the magnesia may combine with the 

 silex, and the potash evaporate j so that felspar and magnesia may 

 become olivine. 



