Jounston-Lavis—The Eruption of Vesuvius'in April, 1906. 191 
2. Ancient scoric, lapilli, and dust :— 
(d) Fresh and unaltered. 
(e) Same changes as in (6). 
(f) Same changes as in (c). 
3. Ancient ejected blocks of sedimentary origin, and their metamorphic derivatives 
that have again been ejected and again buried, and have been sub- 
jected to the same treatment as («) and (0). 
Whether we examine the gigantic blocks scattered by the late outburst over 
the slopes of the cone, around its foot, or the small lapilli that buried Ottajano, 
we find they have the same characters. The principal ones are composed of 
fragments of dyke-rocks or lavas. Many are as fresh when broken as the day 
they originally cooled; some have undergone partial fusion; and others again have 
had their open fissures or cavities filled by a black glass. Such blocks were fairly 
frequent in the last eruption. Sometimes this black glass entirely fills the cavity, 
sometimes only in part, being insufficient in quantity to do so, or being blown up 
by bubbles.* I have in my collection a specimen of an old cavernous lava, in 
which the black glass hangs from what was the roof as a great thick blob or 
stalactite, showing its great viscosity at the moment it reached that situation. 
I have arranged in the following Table the analyses published by Signor 
Matteucci. t 
* In one specimen I collected of this eruption a cavity is lined, or coated, with this black glass, from 
which some remarkably limpid and well-terminated leucites have separated. 
+ Op. cit., p. 851. 
[ TABLE. 
