It is probable that few spots on the earth are more subject to earthquakes than this little isle. It is not a rare occurrence to have two or three in the month; and I am informed that in the summer of 1811, for thirty or forty successive days, it was usual to experience several shocks each day. The occasional violence of these earthquakes is testified by the breaches in the castle walls, and by cracks in different buildings of the city. Their sphere seems to be very limited, seldom extending beyond the isles in the vicinity, and some parts of the neighbouring continent; and occasionally, as it appears, still more entirely confined to this island. From the information i was able to collect here, the motion or sense of motion in these earthquakes is described to be more frequently that of undulation than of vibration or concussion; a mode of action which it is difficult to reconcile with any of the common agencies of physical force by impulse. It was further stated to me at Zante, and the statement is confirmed by the history of earthquakes elsewhere, that their occurrence is usually preceded by a peculiar state of the air; which some describe as a heaviness or oppressiveness; others with the stronger expression of a sulphureous atmosphere; and this, as it appears, independently of the season of the year. Another remarkable fact is, that they are generally followed by rain, a statement which I received on good authority as well at Zante as at Santa Maura, and on the continent of Albania. It is not easy to account for such circumstances with the idea of a single local action; and were I to venture an opinion on the subject, I should think it much more probable that earthquakes are an electrical phenomenon; the effect of electrical movement and distribution, rather than the result of any direct chemical agency, as seems to have been generally surmised. That great electrical inequalities and changes do occur in the body of the earth is rendered by analogy very probable; and a reference to such changes will best explain the occasional extent of earthquakes, their more frequent occurrence in warm climates, the nature of the motion, and the atmospherical phenomena which precede and follow them. Fewer lights have yet been thrown on this subject than might perhaps have been expected from the general progress of science.
