d of the sea had been lifted up
bodily.

The solid products, says Dr. John Davy, whether they consisted of sand,
light cinders, or vesicular lava, differed more in form than in
composition. The lava contained augite; and the specific gravity was
2.07 and 2.70. When the light spongy cinder, which floated on the sea,
was reduced to fine powder by trituration, and the greater part of the
entangled air got rid of, it was found to be of the specific gravity
2.64; and that of some of the sand which fell in the eruption was
2.75;[600] so that the materials equalled ordinary granites in weight
and solidity. The only gas evolved in any considerable quantity was
carbonic acid.[601]

_Submarine eruptions in mid-Atlantic._--In the Nautical Magazine for
1835, p. 642, and for 1838, p. 361, and in the Comptes Rendus, April,
1838, accounts are given of a series of volcanic phenomena, earthquakes,
troubled water, floating scoriae and columns of smoke, which have been
observed at intervals since the middle of the last century, in a space
of open sea between longitudes 20 degrees and 22 degrees west, about
half a degree south of the equator. These facts, says Mr. Darwin, seem
to show, that an island or an archipelago is in process of formation in
the middle of the Atlantic; a line joining St. Helena and Ascension
would, if prolonged, intersect this slowly nascent focus of volcanic
action.[602] Should land be eventually formed here, it will not be the
first that has been produced by igneous action in this ocean since it
was inhabited by the existing species of testacea. At Porto Praya in St.
Jago, one of the Azores, a horizontal, calcareous stratum occurs,
containing shells of recent marine species, covered by a great sheet of
basalt eighty feet thick.[603] It would be difficult to estimate too
highly the commercial and political importance which a group of islands
might acquire, if in the next two or three thousand years they should
rise in mid-ocean between St. Helena and Ascension.

CANARY ISLANDS.

_Eruption in Lancerote, 1730 to 1736._--The effects of an eruption which
happened in Lancerote, one of the Canary Islands, between the years 1730
and 1736, were very remarkable; and a detailed description has been
published by Von Buch, who had an opportunity, when he visited that
island in 1815, of comparing the accounts transmitted to us of the
event, with the present state and geological appearances of the
country.[604] On the 1st