Geol. Mag. IflOO. 



Plate XXV. 



haso VII, period 1, Pumpeii eruptiou 

 of A.]). 79, to illustrate same 

 dilfereuce as last Plate. 



Dr. H. J. Jo!int>lon-L<wis microphol 



Pumices and Pumiceous Scoria from explosive eru[)tioii.s, Monte Somma 

 and Vesuvius. 



