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Show kWFUL HEAT IN VOLCANOES Melted Rock Attains a Temperature 1600 Degrees F In a recently published volume on vol- r.it,o. prof ' I 1 r undertakes to t.-ll why volcanoes have eruptions. Melted rock such aa Is thing from Vesuvius re-Qiilr. re-Qiilr. a temperature of 1sO0 degrees Fahrenheit, Fah-renheit, so that It becomes liquid only far down In the earth perhsips sixty or ion miles. Below the outer crust of cooled and solidified rocks there must b a larger lone of rock which still remains solid, because its tempvruture Is less than that of the melting point corresponding to the pressure under which It rests, and below that again there must be rock or magna In a state of fusion, it Is to this magna that Prof Doelter looks for the primary source of volcanic activity. At the same time the depth at which this primary re.,-r ..ii ..f magna lies and the pressure under which It Is Confined are so great that a direct eruption from It Is Inconceivable, Incon-ceivable, but when by movements In the overlying crust or otherwise a channel Ih opened the magna may rise to a depth where It Is surrounded by rock at a lower tt-miK.-rature than the melting point In these circumstances solidification begins. From nil volcanoes large quantities of steam, of carbonic add and other gases are evolved, and the course of every' lnva stream Is marked by clouds of steam evolved from the cooling lavs. At one time and the Idea Is still common--thls steam was supposed to have been derived from sea wati r which has obtained uccews to the molten lava while still underground, under-ground, but this explanation Is now generally gen-erally rejected! being Impossible In some cases and Inadequate in all. and the greater great-er part of the steam and other emanations emana-tions from a volcano arc nqw regarded B4 directly derived from an original store In the interior of the earth. However this mas he. It Is certain thut the magna from which volcanic luva is derived Is not merely In a stale of Igneous fusion, but Is combined with water and gases which are given off as it solidifies, and by their escape es-cape on the surface of lava streams. |