522 
DRS. T. ANDERSON AND J. S. ELETT ON THE ERUPTIONS OF THE 
before we arrived in St. Vinc'ent, and we directed a considerable amount of attention 
to the evidence in favour of it and against it while engaged in our work on the 
Soufriere. It cannot be denied that, especially in St. Vincent, an enormous amount 
of the pre-existing rock around the crater has been blown into the air, and this is 
sufficiently attested by the changes in the conformation of the crater-walls and the 
increased depth of its floor. Angular fragments of the old ashes and lavas, often 
several feet in diameter, are very numerous, and are easily distinguished by their 
form, appearance, and structure from the bombs which originated from this eruption. 
No doubt, also, fine dust of this nature mingled with the cloud, but we saw no 
evidence that any considerable part of the mountain had been shattered to minute, 
almost impalpable, powder, and disseminated through the air l^y the explosions. It 
seemed rather that the older igneous masses had yielded fragments usually of some 
considerable size, and that a breccia, and not a dust cloud, would have been produced 
ill this way. 
The presence of glassy fragments, some of which are full of crystallites, while others 
are practically free from them, may be explained in more than one way. It may be 
that the partly devitiffied material was that which formed the surface and the sides 
of the column of molten lava, the more vitreous substance its centre and deeper parts. 
But we should also lie prejiared to admit that the magma was not entirely homo¬ 
geneous, and that 2 :»arts may have been more liquid, or less crystalline, than others. 
This would have given rise to a lianded structure, such as is so common in the 
vlti'eous lavas, had the mass poured out in a coulee arid rajiidly solidified to form 
an andesitic lava flow. 
It is also possible that the gases may not have lieen quite equally abuudant 
throughout, and to these two causes, conjointly or separately, we may ascribe the 
presence of a considerable number of small vesicular lapilli, and even occasionally of 
immded pieces of pumice mixed with the dust. There was very little pumice in 
8t. Vincent, lint many scoriaceous lapilli with emliedded crystals, while at Pelee 
|)uniice was more abundant, though still not in sufficient quantity to form a 
consideralile proportion of the ejecta. 
In this connection we may remark that in Martinique the eruption of July 9tli 
ejected more vesicular pumiceous glass than any of tlie previous outbursts, and Ave 
have received information from St. Vincent that pumice is more abundant in the 
ashes of September 3rd. It looks as if the magma in these volcanoes Avas 
undergoing some change in its physical condition, and that the highly crystalline 
and comparatiAmly cold condition of the material at first ejected AA'as not quite so 
pronounced in the later stages. What efiect this may haAm on the future phases 
of the volcanic activity Ave can only guess at present, but it is a problem of much 
interest, and Avell Avorthy of careful attention. 
* MM. Lacroix, Roj.liu de e’Isle & Giraud, “ Sur les Roches rejetees par I’Eruption actuelle dc la 
Moiitagne Pelee,” ‘ Comptes Rendirs,’ a^oI. cxxv., p. 452. 
