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Updated: June 25, 2025
Every geologist is aware how often silicified trees occur in volcanic tuffs, the perfect preservation of their internal structure showing that they have not decayed before the petrifying material was supplied. The porous and vesicular nature of a large part, both of the basaltic and trachytic lavas, affords cavities in which silex and carbonate of lime are readily deposited.
The lower surface of the lava is vesicular, but sometimes only to the thickness of a few inches; the upper surface, which is likewise vesicular, is divided into balls, frequently as much as three feet in diameter, made up of concentric layers.
I rather think that the presence of the sun acts upon the propagation and intensity of sound by the obstacles met in currents of air of different density, and by the partial undulations of the atmosphere arising from the unequal heating of different parts of the soil. In calm air, whether dry or mingled with vesicular vapours equally distributed, sound-waves are propagated without difficulty.
Even in an 8 1/2 inch reflector I have frequently seen the outer slope of the large ring-plain on the north-western side of Vendelinus, so perforated with these objects that it resembled pumice or vesicular lava, many of the little holes being evidently not circular, but square shaped and very irregular.
Lava. b. Dikes of vesicular and amygdaloidal lava are also seen traversing marine tuff or peperino, west of Palagonia, some of the pores of the lava being empty, while others are filled with carbonate of lime.
Where the shoals are 8 to 10 degrees colder at their surface than the surrounding sea, it cannot be surprising that they should produce a local change of climate. May not these submarine islands act upon the formation and accumulation of the vesicular vapours in some other way than by cooling the waters of the surface?
Besides the specimen above alluded to, in which we see a fragment becoming slightly cellular, and blending into the surrounding matrix, some of the grains of the steel-blue augite also have their surfaces becoming very finely vesicular, and passing into the nature of the surrounding paste; other grains are throughout, in an intermediate condition.
Sure enough the opening was found, and the boat once more lowered to investigate and find that the coral-reef still spread out like a barrier, but the coral insects were dead, and as they investigated farther it was to find that there was not a single shell-fish of any kind living in the shoal water, nor any trace of life, but on the highest part of the bleached white coral there were a few blocks of blackish-grey vesicular or cindery-looking stone.
It is reiterated ad nauseam in many popular books that the moon is a changeless world, and it is implied that, having attained a state when no further manifestations of internal or external forces are possible, it revolves round the earth in the condition, for the most part, of a globular mass of vesicular lava or slag, possessing no interest except as a notable example of a "burnt-out planet."
Hence we may conclude that the basalt is contemporaneous with the upper parts of the great tertiary formation. The lava where first met with is 130 feet in thickness: it there consists of two, three, or perhaps more streams, divided from each other by vesicular spheroids like those on the surface.
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