ILLUSTRATIONS (3). DEPTHS OF SPRINGS. 379 



strata of the Rocca del Palo actually rise, we must assume 

 that they are upheaved from below by volcanic forces. 



My learned and indefatigable friend, Oltmanns, has pub- 

 lished the details of all these measurements with critical 

 remarks.* Would that this work might incite geognosists 

 f o enter upon a series of hypsometric observations, by which, 

 in the course of time, Vesuvius, which is, excepting Strom* 

 boli, the most accessible of all European volcanos, may be 

 thoroughly understood in all periods of its development. 



(2) p. 371 " At elevations where the pressure is less. 9 ' 



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, aus den J. 182021, s. 99. 



(3) p. 373" Springs which rise from, different depths" 



Compare Arago in the Annuaire du Bureau des Longitudes 

 pour 1835, p. 234. The increase of the temperature is in our 

 latitudes 1 Fahr. for nearly every 54 feet. In the Artesian 

 boring at the New Salt-works (Oeynhausen's Bath) near 

 Minden, which is the greatest known depth that has been 

 reached below the surface of the sea, the temperature of the 

 water at 2231 feet, is fully 91 Fahrenheit, whilst the mean 

 upper temperature of the air may be assumed at 49 '3 Fahr. 

 It is very remarkable that, even in the third century, Saint 

 Patricius, bishop of Pertusa, should have been led, from the 

 thermal springs near Carthage, to form a very correct view 

 of such an increase of heat.t 



* See Abhandl. der Kb'nigl. Akademie der Wissenschqften zu Merlin, 

 Jahr 1822 und 1823, s. 320. 



+ A eta S. Patricii, p. 555, ed. Ruinart; Cosmos, vol. i. p. 220, 

 (Bohn's edition). 



