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Show 398 STRUCTURE .AND .ACTION OF VOLCANOS. upraised by subterranean forces. The accordance of the three measurements between 1773 and 1805 is almost as striking as that of those taken from 1816 to 1822. In the latter period, we cannot doubt the height being from about 621 to 629 toises (3970 to 4022 English feet). Are the measurements made from thirty to forty years earlier, which gave only 606 to 609 toises (3875 to 3894 English feet), less certain? At some future day, after longer periods shall have elapsed, it will be possible to decide what is due to errors of measurement, and what to an actual rise in the margin of the crater. There cannot be in this case any accumulation of loose materials from above. If the solid trachyte-like lava beds of the Rocca del Palo really become higher, we must assume them to be upheaved from below by volcanic forces. My learned and indefatigable friend Oltmanns has placed all the details of the above measurements before the public, accompanied by a careful critical examination of them, in the Abhandl. der konigl. Akademie , der Wissenschaften zu Berlin, 1822-1823, s. 3-20. May this investigation be the means of inducing geologists frequently to examine hypsometrically this low and most easily accessible (except Stromboli) of the European volcanos, so that in the course of centuries there may be obtained a frequently checked and accurate account of its periods of development ! (2) p. 391.-a Whe1·e the pressure is less." Compare Leopold von Buch on the Peak of Teneriffe, in his Physikalische Beschreibung der canarischen Inseln, 1825, s. 213; and in the Abhandlungen der konigl. Akademie zu Berlin, 1820-1821, s. 99. (B) p. 393.-" Waters of springs 1-ising from different depths." Compare Arago in the Annuaire du Bureau des Longitudes pour 1835, p. 234. The increase of temperature is in our latitudes 1 o of Reaumur (2°.25 of a degree of Fahrenheit) for every 113 Parisian feet (120.5 English feet), or 1 o Fah. to 53.5 English feet nearly. In the Artesian boring at NewSalzwerk (Oe,ynhausen's Bad), not far from Minden, which is the greatest known depth below the level of the sea, the temperature of the water at 2094t Parisian feet (2232t Eng.) is fully 26°.2 Reaumur, or 91 o Fahr.; while the |