ANNOTATIONS AND ADDITIONS. 247 



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 3824 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 Boca 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 measurement 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 hypso- 

 metrically this low and most easily accessible (except Strom- 

 boli) of the European volcanos, so that in the course cf 

 centuries there may be obtained a frequently checked and 

 accurate account of its periods of development.! 



( 2 ) p. 235. " Where 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. 



