DOMAIN XII. VOLCANIC. 97 



than it assumes when it only enters the 

 confines of the sea. It always seems to 

 have another singularity, which must not 

 be forgotten, namely, an arid and dead 

 appearance, ranking it with the stones 

 called by the Italians pietri morti; while 

 other substances indescribably belong to 

 what is called the living rock. 



In the opinion, therefore, of the greatest 

 mineralogists, we are only authorised to 

 consider as compact lavas those which 

 have very small pores; for volcanic ba- 

 saltin, though admitted by Dolomieu and 

 Spallanzani, is exposed to all the tempests 

 of Neptune and his followers. Masses and 

 columns of basaltin, brought from well 

 known lavas of whatever antiquity, would 

 alone form a barrier against their attacks. 

 A strict examination of the supposed ba- 

 saltic columns of Etna, where its vast lavas 

 enter the sea, might also lead to some con- 

 clusions, whether the opinion of those phi- 

 losophers be just, who argue that basaltin 

 is always a volcanic product, its compact- 

 ness arising from its formation under the pri- 





