•*• *Sv 



find 

 We 



tyeja 



Sty. 



H 



i 



orioi 





Pi, 

 soria, 



no 



r 



h On 

 omerate, 



1 closely 



ed to be 



infusoria 

 nd often 



already 



1 50 feet 



ine, near 



?eumula- 



ive been 

 sin the 



•al otto 

 ibserM 



sliffate? 

 ta sronian 



by 



e 



e 



)Ir. 



>a 



alios, * 







» 



Ch. XXV.] 



INFUSORIAL TUFF 



64-5 



cases of infusoria often half obliterated by the action of 

 heat, and the fine dust thrown out into the air during erup- 

 tions, is sometimes referable to these most minute organic 

 substances, brought up from considerable depths, and some- 

 times mingled with small particles of vegetable matter. 



In what manner did the solid coverings of these most 

 minute plants and animalcules, which can only originate and 

 increase at the surface of the earth, sink down and penetrate 

 into subterranean cavities, so as to be ejected from the vol- 

 canic orifices ? We have of late years become familiar with 

 the fact in the process of boring Artesian wells, that the 

 seeds of plants, the remains of insects, and even small fish, 

 with other organic bodies, are carried in an uninjured state by 

 the underground circulation of waters, to the depth of many 

 hundred feet. With still greater facility in a volcanic region 

 we may conjecture, that water and mud full of invisible in- 

 fusoria may be sucked down, from time to time, into subter- 

 ranean rents and hollows in cavernous lava which has been 

 permeated by gases, or in rocks dislocated by earthquakes. 



It often happens that a lake which has endured for centuries 

 in a volcanic crater, disappears suddenly on the approach of 



a new eruption. Violent shocks 



agitate 



the 



region, and ponds, rivers 



and wells are dried up. 



surrounding 



Large 



cavities far below may thus become filled with fen-mud chiefly 

 composed of the more indestructible and siliceous portions 

 of infusoria, destined perhaps to be one day ejected in a 

 fragmentary or half-fused state, yet without the obliteration 

 of all traces of organic structure.*" 

 Herculaneum. — It was remarked that no lava has flowed 



* See Ehrenberg, Proceedings (Be- 

 richte) of the Royal Acad, of Sci. Berlin, 

 1844, 1845, and an excellent abstract of 

 his papers by Mr. Ansted in the Quart. 

 Journ. of the Geol. Soc. London, No. 7. 

 Aug. 1846. In regard to marine infu- 

 soria found in volcanic tuff, it is well 

 known that on the shores of the island 

 °f Cephalonia in the Mediterranean 

 (Proceedings, Geol. Soc. vol. ii. p. 220) 

 there is a cavity in the rock, into which 

 the sea has been flowing for ages, and 



bottom of the ocean. The marine cur- 

 rent has been rushing in for many years, 

 and as the infusoria inhabiting the 

 waters of the Mediterranean are ex- 

 ceedingly abundant, a vast store of their 

 cases may accumulate in submarine ca- 

 verns (the water, perhaps, being con- 

 verted into steam, and so escaping up- 

 wards), and they may then be cast up 

 again to furnish the materials of vol- 

 canic tuff, should an eruption occur like 

 that which produced Graham Island, off 



toany others doubtless exist in the leaky the coast of Sicily, in 1831 . 



