t512 INCIDElSrTAL EFFECTS OF HUMAIf ACTION. 



When the opening was made, fluid lava poured forth and flowed 

 rapidly towards Paterno ; but the inhabitants of that place, not 

 caring to sacrifice their own town to save Catania, rushed out in 

 arms and put a stop to the operation." * In the eruption of 

 Yesuvius in 1Y94, the viceroy saved from impending destruction 

 the town of Portici, and the valuable collection of antiquities 

 then deposited there, but since removed to Naples, by employing 

 several thousand men to dig a ditch above the tovm, by which 

 the lava current was carried off in another direction.f 



Incidental Effects of Humcm Action. 



I have more than once alluded to the collateral and unsought 

 consequences of human action as being often more momentous 

 than the direct and desired results. There are cases where such 

 incidental, or, in popular speech, accidental, consequences, though 

 of minor importance in themselves, serve to illustrate natural 

 processes ; others, where, by the magnitude and character of the 

 material traces they leave behind them, they prove that man, in 



the orifice upwards with great velocity, like the water from a fountain, in a 

 stream eight or ten feet in diameter, throwing up occasionally volcanic bombs 

 three or four feet in diameter, which exploded at the height of eight or ten 

 yards, but it immediately spread out on the declivity down which it flowed, 

 to the width of several yards. It continued red-hot in broad daylight, and 

 without a particle of scoriae on its surface, for a course of at least one hun- 

 dred yards. At this distance, the suffocating, sulphurous vapors became so 

 dense that I could follow the current no farther. The undulations of the 

 surface were like those of a brook swollen by rain. I estimated the height of 

 the waves at five or six inches by a breadth of eighteen or twenty. To the 

 eye, the fluidity of the lava seemed as perfect as that of water, but masses of 

 cold lava weighing ten or fifteen pounds floated upon it like cork. 



The heat emitted by lava currents seems extremely small when we consider 

 the temperature required to fuse such materials and the great length of time 

 they take in cooling. I saw at Nicolosi ancient oil- jars, holding a hundred 

 gallons or more, which had been dug out from under a stream of old lava 

 above that town. They had been very shghtly covered with volcanic ashes 

 before the lava flowed over them, but the lead with which holes in them had 

 been plugged was not melted. The current that buried Mompiliere in 1669 

 was thirty-five feet thick, but marble statues, in a church over which the lava 

 formed an arch, were found uncalcined and uninjured in 1704 See Scropb, 

 Volcarwes, chap, vi., § 6. 



* Fekbaka, DescrizioTie dell 'Etna, p. 108. 



f Lakdqrebe, Naturgeschichte der Vulhane, ii., p. 83. 



