114 PLINY'S NATURAL HISTORY. [Book II.
CHAP. 83. (81.) — SIGNS OF AN APPROACHING EARTHQUAKE.
There is no doubt that earthquakes are felt by persons on shipboard, as they are struck by a sudden motion of the waves, without these being raised by any gust of wind. And things that are in the vessels shake as they do in houses, and give notice by their creaking; also the birds, when they settle upon the vessels, are not without their alarms. There is also a sign in the heavens; for, when a shock is near at hand, either in the daytime or a little after sunset, a cloud is stretched out in the clear sky, like a long thin line[1]. The water in wells is also more turbid than usual, and it emits a disagreeable odour[2].
CHAP. 84. (82.) — PRESERVATIVES AGAINST FUTURE EARTHQUAKES.
These same places[3], however, afford protection, and this is also the case where there is a number of caverns, for they give vent to the confined vapour, a circumstance which has been remarked in certain towns, which have been less shaken where they have been excavated by many sewers. And, in the same town, those parts that are excavated[4] are safer than the other parts, as is understood to be the case at Naples in Italy, the part of it which is solid being more liable to injury. Arched buildings are also the most safe, also the angles of walls, the shocks counteracting each other; walls made of brick also suffer less from the shocks[5]. There is also a great
1 This observation is taken from Aristotle, Meteor. ii. 8.
2 Phænomena of this kind have been frequently noticed, and are not difficult of explanation.
3 "In iisdem;" "Iidem, inquit, putei inclusum terra spiritum libero meatu emittentes, terræ motus avertunt." Alexandre in Lemaire, i. 406.
4 "Quæ pendent." M. Ajasson translates this passage, "qui sont comme suspendues." Hardouin's explanation is, "Structis fornice ca- meris imposita ædificia intelligit; quod genus camerarum spiramenta plerumque habet non pauca, quibus exeat ad libertatem aer." Lemaire, i. 407.
5 Many of these circumstances are referred to by Seneca, Nat. Qæst. vi. 30. On the superior security of brick buildings, M. Alexandre remarks, "Muri e lateribus facti difficihus quam cæteri dehiscunt, unde fit ut in urbibus muniendis id constructionum genus plerumque præ- feratur. Ex antiquæ Italiæ palatiis templisve nihil fere præter immensas laterum moles hodie superest."
