VOL. XXXVIII.] PHILOSOPHICAL TRANSACTIONS. 607 



March p, 1 730-1 , o. s. at 4 in the afternoon, there was an earthquake almost 

 all over the kingdom of Naples, but it was felt most in Apulia. While it last- 

 ed, all those appearances mentioned by the ancients, were observed here also : 

 as first a tremor ; then a pulse ((npuT^uc?) according to Aristotle, or a succussa- 

 tion, as Possidonius from Seneca calls it ; and last of all an inclination, or a 

 nutation of the earth, like that of a ship, as it were. These various motions 

 succeeded each other alternately for 3 minutes and a few seconds. At that time 

 the air was overcharged with dense, low, and immovable clouds, which were 

 afterwards dissipated by a gentle northerly wind. Next day the sun shone more 

 languid, as if he had been covered with very thin clouds, though there were 

 then none in the heavens. This phenomenon was also observed in the follow- 

 ing stronger shocks. The fishermen near the shore observed the sea swell sud- 

 denly, and they weathered out a storm from Siponte and Barletta, that is, 

 nearly, from the north, without any wind, but not without apprehensions of 

 being ship-wrecked. 



March 10, at 8 in the forenoon, there happened a new, but a shorter and 

 weaker earthquake, in the same province ; but not so weak but that it was felt 

 at Naples. This was preceded by a kind of accension, or short coruscation, 

 about Mount Garganus, observed by the inhabitants of Terra di Bari, and 

 which insensibly vanished into smoke or darkness. In the parts about Foggia a 

 strong N. E. wind generally preceded this second earthquake, as also the others 

 that happened afterwards in April, October, and November; though sometimes 

 the air was quite calm. The number of houses that fell, and of men buried in 

 their ruins, was considerable ; not less than 600. The town of Foggia seemed 

 to be the centre of these shocks : for, there the shocks and downfall of the 

 houses were most considerable ; and from thence they diffused themselves to 

 more remote places, the impetus gradually remitting ; so that it may be said 

 that the propagation of this earthquake was successively diminished (unless the 

 different solidity and interruption of the interjacent earth caused any alteration) 

 in the duplicate ratio of the distances, according to the common laws of nature 

 in many other things ; which was carefully observed in the oscillations of pen- 

 dulums placed at different distances from Foggia : for pendulums of a palm in 

 length at Ascoli di Satriano, and at Giovenazzo, applied to a graduated semi- 

 circle, and moving in the concussions of the earth, erred more or fewer de- 

 grees from the centre of oscillation, according as they were more or less distant 

 from Foggia : for, the number of these degrees (greater in the nigher Ascoli, 

 and less in the remoter Giovenazzo) answered nearly to the duplicate ratio of 

 the distance of these places from the centre of the earthquake: and hence it 



