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Show 466 SUMMARY OF THE CONTENTS. ideas, and the progress of physical geology. Influence of the form of the Mediterranean on the earliest ideas respecting volcanic phenomena. Comparative geology of volcanos. Periodical recurrence of certain natural changes or revolutions which have their origin in the interior of the globe. Relative proportion of the height of volcanos to that of their cones of ashes in Pichincha, the Peak of Teneriffe, and Vesuvius. Changes in the height of the summit of volcanos. Measurements of the height of the margins of the crater of Vesuvius, from 1773 to 1822: ·the author's measurements comprise the period from 1805 to 1822 375-386 Particular description of the eruption in the night of 23-24th October, 1822. Falling in of a cone of cinders 426 English feet in height, which previously stood in the interior of the crater. The eruption of ashes, from the 24th to the 28th of October, is the most remarkable of which we possess any certain knowledge since the death of the elder Pliny 386-390 Difference between volcanos with permanent craters : and the phenomena (very rarely observed within historic times) in which trachytic mountains open suddenly, emit lava and ashes, and reclose again perhaps for ever. The latter class of phenomena are particularly instructive to the geologist, because they recall the earliest revolutions of the oscillating, upheaved, and fissured surface of the globe. They led, in classical antiquity, to the view of the Pyriphlegethon. Volcanos are -intermitting earth springs, indicating a communication (permanent or transient) between. the interior and the exterior of our planet; they are the result of a reaction of the still fluid interior against the crust of the earth; it is therefore needless to ask what chemical substance burns, or supplies materials for combustion, in volcanos 390-393 The primitive cause of subterranean heat is, as in all planets, the process of formation itself, i. e. the forming of the aggregating mass from a cosmical gaseous fluid. Power and influence of the radiation of heat from numerous open fissures and unfilled veins in the Ancient world. Climate (or atmospheric. temperature) at that period very independent of the geographical latitude, or of the position of the planet in respect to the central body, the sun. Organic forms of the present tropical world buried in the icy regions of the north. 393-394 Scientific elucidations and additions-p. 395 top. 399. Barometric measurements of Vesuvius. Comparison of the height of different points of the crater of Vesuvius. 395-398 Increase of temperature with depth, 1° Reaumur for every 113 Parisian feet, or 1° of Fahrenheit for every 53.5 English feet. Temperature of the Artesian well at Oeynhausen's Bad (New Salzwerk, near Minden), the greatest depth yet reached below the level of the sea. The hot springs near Carthage led Patricius, Bishop of Pertusa, in |