438 DOMAIN XII. VOLCANIC. 



been sufficiently described: I shall only add, 

 that it is found in considerable quantities in 

 Campo Bianco ; but solely in detached pieces, 

 and not forming currents or veins; whence it is 

 evident that it has been ejected from the volcano, 

 and has not flowed in the manner of lava. 



* c The second species is cut by the labourers 

 in parallelepipeds, about twenty-two inches long 

 and eight broad. This pumice is of a dark dirty 

 * colour, contains no extraneous bodies, gives a few 

 sparks with steel, and is so light that some pieces 

 of it will float on the water. It is formed by 

 agglomeration of pumiceous bubbles, which are, 

 as it were, conglutinated together, and incline 

 more or less to an oblong figure. To detail 

 their various sizes would be useless prolixity. I 

 shall only say, that from the very minute and, if 

 I may so term them, infinitesimal, they increase 

 in size till some of them exceed an inch in dia- 

 meter, though the latter are less numerous than 

 the former. They are all extremely friable, as 

 their sides are very thin, and always semi-vitre- 

 ous. The glass of many of them is white, and 

 has some transparency ; but in others is dull, 

 and almost entirely opake. 



" As I do not know that this species of pu- 

 mice has ever been described before, though it 

 certainly well deserves attention, I would wish 





