194 Jounsron-Lavis—The Eruption of Vesuvius in April, 1906. 
cooled magma. ‘The vesicles are sometimes so small as to give the mass the 
appearance of a fine sandstone, and in others reaching a size in which the fist 
can be placed. Under the microscope several mineral species have been described 
—quartz, diopside, wollastonite, by M. Lacroix; and in some I found felspars. 
I consider these masses to be similar to the black-glass fillings above described, 
but which in this case had contained H,O, and had vesiculized by expansion as 
pressure was relieved. 
The next class either consists of pieces of old lavas, fissured or cavernous, or 
is more frequently composed of fragments of lavas, scoriz, and lapilli adhering 
together. The cavities or interspaces of these imperfectly agglomerated masses 
are lined by a series of interesting minerals that have been deposited therein at a 
later date to the emplacement of these fragmentary materials near the volcanic 
chimney, from which position they were eventually torn and ejected in this 
eruption. 
Some of these specimens are rather striking, as their interspaces are crowded 
with long, slender, black, needle-like prisms of amphibole. Others glisten with 
numerous glassy or white crystals covering all free surfaces. ‘The minerals so 
occurring have been elaborately studied by M. Lacroix* and Sig. Zambinellit 
from the mineralogist’s point of view. I give here a list of the minerals so far 
recorded :— 
Orthoclase. Dayvyne. Magnetite. 
Acid Oligoclase.+ Microsommite. Hematite. 
Anorthite.+ Hornblende. Fluorite. 
Leucite. Augite. Apatite. 
Sodalite. fEgirine. Anhydrite. 
Cavolinite. Garnet.+ Sphene.+ 
Nepheline. Biotite. 
Those minerals without a cross I have observed myself, and those so marked 
have been detected either by M. Lacroixt or by Sig. Zambinelli, and I shall not 
therefore further refer to them in detail. Suffice it to say that they show a 
striking resemblance to those produced under similar conditions in 1872, and so 
carefully studied by A. Scacchi. 
The order of their deposition in most cases seems to have been—orthoclase and 
other felspars; then the augites and hornblendes; next the felspathoids. The 
* Op. cit. 
} ‘Notizie mineralogiche sull’ eruzione Vesuviana dell’ Aprile, 1906.”—Atti d. R. Accad. d. Se. fis. 
e mat. di Napoli, vol. xiii., serie 2*, Novembre, 1906, 
$ Op. cit, 
