M. Fouqué estimated that the discharge of steam from a merely parasitic cone of Etna during 100 days was equal to 2,100,000 cubic meters of water. If this were ground-water, and the lava from which it issued had an excess of 500° Fahr. above the fusion-point, the formation of this steam would congeal a column 400 feet in diameter and 3000 feet deep in the time given. If this case is typical, and if Fouqué’s estimate is not greatly exaggerated or very exceptional, the view that any large portion of the steam from volcanoes comes from surface-waters seems to be incompatible with the persistence of ebullition and explosion which many of them exhibit. Stromboli has been in constant eruption as far back as the history of the region runs. It is now exploding every three to ten minutes, and yet the mass of lava seems to be small and its outflow inconsiderable. Is it possible that a current of steam, given out with this activity for so long a period, was derived from adjacent ground-waters, and has not yet solidified the lava?
The problem takes on a very different aspect if the steam, or at least some large part of it, rises from great depths and brings thence an excess of heat. It then becomes an agency for the maintenance of the liquidity of the lava, for giving it convective motion, and for promoting explosive action, so long as it continues to rise.
For these and other reasons the balance of present evidence seems to us to favor the view that most of the steam and other gases come with the lava from its original source deep in the earth.
References on vulcanism.—G. P. Scrope, Volcanoes, London, 1872. R. Mallet, on Volcanic Energy, Phil. Trans., 1873. C. Darwin, Geological Observations on Volcanic Islands, London, 1876. E. Reyer, Beitrag zur Physik der Eruptionen, Vienna, 1877; Theoretische Geologie, 1888. Fouqué, Santorin et ses Éruptions, Paris, 1879, Sartoris von Waltershausen and A. von Lasaulx, Der Aetna, Leipzig, 1880. C. E. Dutton, Geology of the High Plateaus of Utah, U. S. Geog. and Geol. Surv., 1880; The Hawaiian Volcanoes, Fourth Ann. Rept. U. S. Geol. Surv., 1883. Judd, Volcanoes, 1881; The Eruption of Krakatoa (Com. of the Roy. Soc.), 1888. J. D. Dana, Characteristics of Volcanoes, 1890. H. J. Johnston-Lavis, The South Italian Volcanoes, Naples, 1891. E. Hull, Volcanoes, Past and Present, 1892. Milne and Burton, The Volcanoes of Japan, 1892. J. P. Iddings, The Origin of Igneous Rocks, Bull. Phil. Soc., Washington, Vol. XII, 1892. A. C. Lane, Geologic Activity of the Earth’s Originally Absorbed Gases, Bull. Geol. Soc. Am., Vol. V, 1894. A. Geikie, Ancient Volcanoes of Great Britain, London, 1897. I. C. Russell, Volcanoes of North America, 1897. T. G. Bonney, Volcanoes, Their Structure and Significance, New York (and London), 1899. F. Miron, Étude des Phénomènes Volcaniques, Paris, 1903. G. C. Curtis, Secondary Phenomena of the West Indian Volcanic Eruptions of 1902, Jour. Geol., Vol. XI, No. 2, 1903. A. Heilprin, Mont Pelée and the Tragedy of Martinique, Philadelphia (and London), 1903. Robert T. Hill, Report on the Volcanic Disturbances in the West Indies, Nat’l Geog. Mag., Vol. XIII, No. 7, 1902. I. C. Russell, The Recent Volcanic Eruptions in the West Indies, Nat’l Geog. Mag., Vol. XIII, No. 7, 1902; Volcanic Eruptions on Martinique and St. Vincent, Nat’l Geog. Mag., Vol. XIII, No. 12, 1902. J. S. Diller, Volcanic Rocks of Martinique and St. Vincent, Nat’l Geog. Mag., Vol. XIII, No. 7, 1902. W. F. Hillebrand, Chemical Discussion of Analyses of Volcanic Ejecta from Martinique and St. Vincent, Nat’l Geog. Mag., Vol. XIII, No. 7, 1902. E. O. Hovey, The Eruptions of La Soufrière, St. Vincent, in May, 1902, Nat’l Geog. Mag., Vol. XIII, No. 12, 1902.
CHAPTER XI.
THE GEOLOGIC FUNCTIONS OF LIFE.
I. THE DISTINCTIVE FEATURES OF ORGANIC PROCESSES.
There is no reason to suppose that life processes, as we know them, were in operation in the earliest stages of the earth’s history. They were introduced and developed gradually during its progress. With life there came into the processes of the earth’s development three distinctive factors:
A. Certain chemical actions giving rise to compounds that are not known to occur independently of life.
B. Certain modes of aggregation of material, and certain kinds of bodily movements, not known except in association with life.