THE REVOLUTIONS OF THE CRUST OF THE EARTH. 301 



peared into the sea on the 28th of December, 1831. Fr. Hoffmann was 

 at that time in Sicily, aDd made a report of it in the Annates de Poggen- 

 dorf. It was the origin of his theory of the accumulation of volcanic 

 ashes. Spratt announced in 1802 that the island again arose from the 

 deep, and that it was hardly three meters or ten feet above the level of 

 the sea.* 



Submarine eruptions are quite frequent. The navigators who have 

 observed them describe the phenomenon in brilliant colors and with a 

 vivacity of expression, which evinces the powerful impression made 

 upon their minds. In fact, the boiling sea, the blackened waters thick 

 with ashes, the boisterous waves, the rise and fall of the columns of 

 water shot into the air, the rumbling of thunder from the electrified 

 clouds, form a wild but harmonious picture, of which it is difficult to 

 catch the details, on account of the constant and rapid change of scene. 



Continental eruptions in the midst of a large plain are not more rare. 

 Humboldt has left a description of the eruption which formed the 

 volcano Jurullo. Six days' journey from the city of Mexico, a large 

 plantation of wheat was agitated for two months by a violent trembling 

 of the earth. Finally it began to undulate like a sea under the influence 

 of a strong wind, and a thousand mouths were opened vomiting flames 

 and lava. Then arose, with six other elevations, the volcano called 

 Jurullo, which soon attained a height of 520 meters (1,700 feet) and 

 vomited torrents of lava.f 



The hot springs, the geysers, seem to have direct connection with 

 earthquakes and volcanic phenomena. The hot springs of Western 

 Bohemia, during the earthquake of Lisbon, experienced several times a 

 loss of water, alternating with an increase of double their usual supply. 

 At the same time several lakes of Carneole became suddenly dry, but 

 filled of themselves a short time after. The same phenomenon was 

 observed several times in Calabria and in America during volcanic 

 eruptions. This phenomenon may be explained in several ways, but 

 we confine ourselves to the following solution, which is sustained by a 

 large number of well-established facts : 



It appears, from the observations of Dr. Cartellieri upon the variation 

 in the supply of the spring called Franzensqiidle at Eger,* that this 

 supply is in inverse proportion to the barometric pressure. This fact 

 admits of the following deductjon. We must suppose, antecedently, a 

 constant force, which causes the water to spout up from the spring, and 

 this force must be independent of the barometric pressure, for if it were 

 not, it would not act in a contrary direction. We may then compare 

 this phenomenon to a fountain in a vacuum, placed under the receiver ot 

 a pneumatic pump, in which the air may be alternately compressed and 



* Ch. Ehrenberg, Die bti Sicilien 8tch neuerlichat wieder hebende Ferdinandea Insel, 



Berliner Monatsberichte. 1863, p. 486, 489. 



tL. Figuier, La Tare avant It Deluge, p. 372. # 



fNowak, Sitzungsberichte der lohmischen Gtstlhcliaft ;/<;■ 11 issenschaften, Prag, 1864, t. 1, 



p. 144. 



