STRUCTURE, AND ACTION OP VOLCANOS. 



upraised by subterranean forces. The accordance of the three mea- 

 surements 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 fre- 

 quently to examine hypsometrically this low and most easily acces- 

 sible (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 ! 



( 3 ) p. 391. "Where the pressure is less" 



Compare Leopold von Buch on the Peak of Teneriffe, in his Phy- 

 sikalische Beschreibung der canarischen Inseln, 1825, s. 213 ; and 

 in the Abhandlungen der konigl. Akademie zu Berlin, 1820-1821, 

 s. 99. 



( 3 ) p. 393. "Waters of springs rising 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 of 

 Reaumur (2. 2 5 of a degree of Fahrenheit) for every 113 Parisian 

 feet (120.5 English feet), or 1 Fah. to 53.5 English feet nearly. 

 In the Artesian boring at New Salzwerk (Oeynhausen's Bad), not 

 far from Minden, which is the greatest known depth below the level 

 of the sea, the temperature of the water at 2094 Parisian feet 

 (2232 1 Eng.) is fully 26.2 Reaumur, or 91 Fahr. } while the 



