Page:Popular Science Monthly Volume 50.djvu/254

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240
POPULAR SCIENCE MONTHLY.

structures underlying psychological processes will be found to account for the presence of the extraordinary talents of idiots savants. It is questionable whether Heinecken, the "child of Lübeck," should be included among any of the cases described here. He died too soon (at the age of four years) for the fact of mental weakness of any kind to be established; but his precocity made him the wonder of his time (1731–’25). He knew the chief incidents of the Pentateuch at the age of one year, had mastered all of sacred history at two years, and was intimately acquainted with modern and profane history and geography, and spoke French and Latin, besides his native tongue, at the age of three. Surely such precocity as this must have been due to extraordinary aggregations of gray matter in parts of the brain of a truly abnormal character.

 

IGNEOUS INTRUSIONS AND VOLCANOES.
By ISRAEL C. RUSSELL,

PROFESSOR OF GEOLOGY IN THE UNIVERSITY OF MICHIGAN.

MANY geologists have watched the action of volcanoes in eruption, and have gazed into their craters when in a state of mild activity. One of the most striking of the phenomena revealed at such times is that great volumes of steam are given off from the molten lava which rises in the craters. This steam either escapes quietly, as in the case of the Hawaiian volcanoes, or with explosive violence, as in eruptions of the Vesuvian type. It is now conceded by probably all students of volcanoes that the proximate cause of the violent explosions accompanying many volcanic eruptions is the sudden escape of highly heated steam. Most modern theories advanced to account for volcanic phenomena are based on the assumption that steam is the propelling force which causes the lava to rise from deeply seated sources and to be extruded at the surface. Steam contained in the molten lava is thought by Shaler and others to cause the molten rock to rise and overflow, in much the same way that carbonic acid generated in dough causes it to expand, or as the carbonic acid in ale makes it overflow when the cork of a bottle in which it is contained is withdrawn. In these theories, heat is considered as the prime source of energy, and that, given the heat, steam will be generated which will force the lava to the surface.

I do not wish to criticise the theories that have been advanced, or even to attempt to review them, but simply to change the point of view from which volcanoes have commonly been studied, in the hope that the phenomena observed will group themselves in another and perhaps more instructive way. Current theories are