[55] About ninety species of mollusk shells and the hard parts of echinoderms and crustaceæ have been found in the Palagonite of Sicilian Aci Castello. Lime, for the use of the shell-builders, enters into the composition of such tuffs generally, and the percentage depends upon the percentage of shells. Silica is extracted from it by carbonic acid and sulphuretted hydrogen; and this mineral again depends upon the included quantity of infusorial skeletons. Professor Quekett, Dr Gulliver, and other authorities, have examined specimens of Icelandic Palagonite, in which they could not detect infusoria nor their skeletons, even after boiling in nitric acid.
[56] The word “trap” will be used in these pages to denote the lavas ejected by submarine volcanoes.
[57] Until late years the general opinion was that all basalts are of igneous formation. The contrary has been supported by Mr H. P. Malet (Geogr. Mag., August 1874), to mention no others: he finds in that of Rossberg and the “Rowley Rag” vegetable, animal, and earthy particles which, passed through the fire, would have vanished in vapour. The distinction, therefore, between basalt and basaltic lava becomes fundamental. Granite, again, is by the same writer taken from Hutton and returned to Werner. The author could not but observe, when travelling in the basaltic Haurán, in that Bashan which, according to some, gave a name to the mineral, that the dried mud split under the sun into lozenges and pentagonal flakes (Unexplored Syria, i. 215). Upon this subject more will be said in Chapter XIV.
[58] Forchhammer considered this trachyte an unknown variety of felspar, and called it Baulite.
[59] See Chapter XI.
[60] The date “revealed to Moses” has long delayed the progress of science, and the 6000 years or so, still linger in the orthodox brains. The Hindus and the Moslems were far wiser, or rather better informed; the latter provide for the countless Æons of the past by the theory of Pre-Adamite kings and races.
[61] The Jökull (plur. Jöklar) is explained passim. Suffice it here to say, that it is a mass of eternal ice formed by the enormous pressure of the superincumbent snow; it is not correct, but it is decidedly convenient to render it by “glacier.” The Fell (our “fell,” pronounced Fedl or Fetl) is a single block or peak, and in the plural, a range or sierra; it is mostly free from snow during the summer heats. Fjall (Fyadl, and plur. Fjöll) is the generic term “mons” and κατ’ ἐξοχὴν; it is applied in Icelandic literature to the Alps.
[62] Here is the culminating point of the island, usually assumed at 6500 English feet, more than one-third higher than Vesuvius (4000 feet).
[63] Usually assumed at 6000 English feet.
[64] Generally exaggerated to 5700 English feet.