FLCETZ,ROCKS. countries, it is faid by many mineralogifts to be a volcanic product. This opinion, however, appears to be unfounded ; ift, Becaufe obfidian has never been obferved accompanying lava : 2d, Becaufe it pafles into pitchftone, and is thus conneded with bafalt, clinkftone, felfpar, and clayftone ; 3d, Be caufe it contains a confiderable portion of water of compofition, which is never the cafe with true vol canic rocks. ■ J 1 ' S. Pumice. Bimftein.—Werner. 1. This rock appears alfo to occur in the neweft floetz-trap formation. 2. It was formerly the general opinion, that it was a volcanic produd, becaufe it frequently occurs in countries conjectured to be of igneous forma tion. It is now afcertained to be an aquatic pro- dudt, from the following fadts: 1. It alternates with Neptunian rocks, as bafalt and porphyry ; 2. It is moft diftindly ftratified, and thefe ftrata are fometimes compofed of globular diftind concre tions ; 3. It pafles into obfidian and pearlftone, and is thus conneded with bafalt, pitchftone, porphyry- flate, clayftone, and felfpar; 4. It contains water of compofition, which, as we have juft mentioned, is never the cafe with true volcanic rocks; 5. It has never been obferved to flow in ftreams from the crater or lides of a volcano, and no one ever faw