78 PHILOSOPHICAL TRANSACTIONS. [aNNO ] / 36. 



bladders was, as it were, generated de novo out of the mixture, or else re- 

 covered from being locked up in the body of the metal in an unelastic state. 



This experiment will easily explain a very probable cause of earthquakes, 

 volcanoes, and all fiery eruptions out of the earth ; for nothing more is re- 

 quisite than iron, a vitriolic acid, and water. Now iron is generally found ac- 

 companied with sulphur ; and common sulphur may be analized into an inflam- 

 mable oil, and an acid liquor like oil of vitriol. This acid therefore in the 

 bowels of the earth, by being diluted with a little water, surrounds the iron 

 and works upon it in the same manner as described above ; an effervescence and 

 intesthie heat arise ; the air which comes from the mixture is rarefied, and be- 

 comes very elastic ; its impetus, as it is the more compressed by the incumbent 

 weight of earth, is increased even to an unlimited degree ; and at length, like 

 gunpowder, will remove all obstacles, and exhibit to the spectators above ground 

 the terrible phaenomena of earthquakes and eruptions. Sometimes these in- 

 flammable fumes, if very much heated, as soon as they come to the open air, 

 will catch fire, and so produce those fiery eruptions, of which there are so 

 many instances in the world. 



^n Account of the Storm, Jan. 8, 1734-5. By Mr. Henry Forth. 



N° 442, p. 285. 



At Darlington, 14 miles south from Durham, lat. 54° 46', the evening be- 

 fore the 8th of Jan. 1734-5, Mr. Forth's barometer stood at 29 inches, but 

 had been gradually falling for two days. The wind was then s. w. and of the 

 second degree of strength ; which increased towards midnight a degree more. 

 Most of the day there was snow or sleet. 



The 8th in the morning he found his glass fallen to 28.38 inches, and at 4 

 o'clock p. M. down to 28.05 inches, but by 10 in the evening risen again to 

 28.45 inches. All this while the wind was in the north east, with only a 

 moderate gale, though attended all day with snow, which at night was 2 inches 

 and a quarter deep ; and about 8 it began to freeze. As the wind in the 

 southern parts was all that time in the opposite quarter, Mr. Forth would have 

 expected an accumulation of the air, and as a consequence the rising of the 

 barometer, at the time of its falling the lowest. Had the storm been the night 

 before, when in the northern parts the wind was in the same direction, and had 

 afterwards fallen, he would then have imputed the fall to the quick return of 

 the current of air to restore the equilibrium. 



VJIJUL- iO MjJlU ■ 



