Ixxxvi PROCEEDINGS OF THE GEOLOGICAL soctEry. [Aug. 1902, 
The Names of certain Fellows of the Society were read out for the 
first time, in conformity with the Bye-Laws, Sect. VI, Art. 5, in 
consequence of the non-payment of the Arrears of their Contributions. 
The List of Donations to the Library was read. 
Prof. Bonnry exhibited a mounted specimen of the Volcanic Dust 
which fell on the deck of the steamer Roddam during the great 
eruption of Mont Pelée on May 8th, for which, as well as for another 
from the Soufriére of St. Vincent, that had fallen in Barbados, he 
was indebted to Sir William Crookes, F.R.S. The dust from Mont 
Pelée consists of fragments of minerals and rock (the former, perhaps, 
slightly in excess of the latter), very commonly about ‘007 to 008 inch 
in diameter, but ranging from about -005 to*Olinch. A very little 
fine dust had been removed by levigation before mounting the 
specimen. The minerals are:—(1)Chips of felspar sometimes bounded 
by cleavage-edges, occasionally showing oscillatory twinning or zonal 
structure. ‘lhe refractive index and extinction-angles suggest that 
the majority are labradorite. Some contain minute acicular 
microliths or small brownish enclosures (? vitreous), which now and 
then are regular in form and arrangement, like negative crystals, and 
not seldom contain little bubbles. (2) Pyroxene, occasionally with 
cleavage-edges, or even idiomorphic, eas | a light bottle-green 
tint. There are certainly two species: one showing a distinct pleo- 
chroism from green to brown with straight extinction,—a variety of 
hypersthene; the other barely pleochroic, with an extinction that 
proves it to be augite. He could not identify with certainty 
magnetite or any other mineral. The rock-fragments are chips of a 
brownish, often dirty-looking glass, with small cavities, sometimes 
showing microliths or adhering to minerals; much of it opaque, or 
nearly so, with transmitted light, and a brownish-grey by reflected 
light, once or twice reddish. As Dr. Flett had given an excellent 
description of the Barbados dust from the Soufriere at the previous 
meeting, the present speaker thought that he need say no more 
than that in the specimen now exhibited the fragments seem a 
shade smaller, and minerals are slightly more abundant, especially 
pyroxene, than in the Mont Pelée dust. 
Notwithstanding the risk of generalizing from a single slide, Prof. 
Bonney inferred that the ejecta of the two volcanoes are generally 
similar. Both, compared with specimens in his cabinet from Cotopaxi, 
are more uniform in size. The travelled dust from the Soufriére is 
a little smaller than that from the actual summit of the Andean 
volcano, but coarser than similar material from Chillo (over 20 
miles), Quito (35 miles), Ambato (45 miles), Riobamba (65 miles), 
and the summit of Chimborazo, about the same. All these vary 
much more in size and run distinctly smaller, especially the last.’ 
That from Mattakava, Hick’s Bay, New Zealand (fallen on June 16th, 
1886), is rather coarser, more scoriaceous, with fewer mineral- 
1 All these (collected by Mr. E. Whymper) are described in Proc. Roy. Soc. 
yol. xxxvii (1884) pp. 114 e segg. 
