20 On Volcanos and Earthquakes. 



agitation in one moment, is such a prodigy, as we would never 

 believe, did we not know it to he a fact, from our own senses." 



The astonishment of the writer of this paragraph would 

 have ceased, if he had conceived, as ourselves, that the va- 

 cuum produced in a receiver is almost instantaneous in all 

 its parts, whatever be its extent, or is filled as instantaneous- 

 ly, because steam and gases rush into a vacuum at the rate 

 of thirteen hundred and five feet in a second of time, under 

 the pressure of one atmosphere : what then must it be under 

 eight hundred ? The following extracts will come again in 

 support of this assertion. 



Account of an Earthquake at Lisbon^ Nov. ls<, 1755. Dr. WoJfal. 

 Phil. Tr. vol. 49. 

 " Soon after the shock, (forty minutes past nine,) which was 

 near high water, the tide rose forty feet higher, in an instant, 

 than was ever known, and as suddenly subsided." 



The same at Oporto, in Portugal, JVov. 1st, 1755. Phil. Tr. 



vol. 49. 



"It began about half an hour past nine.. ..and soon saw the riv- 

 er in some places open, and throw out a vast deal of wind, which 

 was very terrifying " 



The same at Cadiz, Nov. \st, 1755. Benjamin Bewick. Phil. Tr. 



vol. 49. 



" Just before ten, the whole town was shaken with a violent 



earthquake they saw rolling towards the city a tide of the sea, 



which passed over the parapet of sixty feet above the ordinary 



level of the water the waves came in this manner four or five 



times, but with less force each time." 



The same in Barbary, Nov. 1st, 1755. General Fowke, Governor 

 of Gibraltar. Phil. Tr. vol. 49. 



At Tetuan, " the earthquake began at ten in the morning...." 



At Tangier, " it began about the same time the sea came up 



to the very walls, a thing never seen before, and went down with 

 the same rapidity. These commotions of the sea were repeated 

 eighteen times, though not with the same violence as at the first 



time The fountains were dried up, so that there was no water 



to be had till night." 



At Arzila, " it happened about the same time." 



