BOOK II. Lxxxiv. 197-LXXXV. 199 



an outlet for the confined breath. Tliis is noticed 

 in whole towns : buildinos pierced by frequent 

 conduits for drainage are less shaken, and also among 

 these the ones erected over vaults are much safer — 

 as is noticed in Italy at Naples, the sohdly built 

 portion of the city being specially liable to collapses 

 of this nature. The safest parts of buildings are 

 arches, also angles of walls, and posts, which swing 

 back into position with each alternate thrust ; and 

 walls built of clay bricks sufFer less damage from 

 being shaken. There is also a great difference in vaneiies oj ■. 

 the actual kind of movement, as the earth shakes in 

 several ways ; there is least danger when it quivers 

 with a trembling rattle of the buildings, and when it 

 rises in a swell and settles back again, with an 

 alternating motion ; also no harm is done when 

 buildings colhde and ram against each other, as 

 the one motion counteracts the other. A waving 

 bend and a sort of billowy fluctuation is dangerous, 

 or when the whole movement drives in one direction. 

 Earthquakes stop when the wind has found an outlet, 

 or else, if they go on, they do not stop before forty 

 days, and usually even longer, some in fact having 

 gone on for one or two years' time. 



LXXXV. I find in the books of the lore of Tuscany Mstorkal 

 that once a vast and portentous earthquake occurred """ "'' 

 in the district of Modena; this was during the 

 consulship " of Lucius Marcius and Sextus Juhus. 

 Two mountains ran together with a mighty crash, 

 leaping forward and then retiring with flames and 

 smoke rising between them to the sky ; this took 

 place in the daytime, and was watched from the 

 Aemih'an road by a large crowd of Knights of Rome 

 vvith their retinues and passers by. The shock 



329 



