Page:Great Neapolitan Earthquake of 1857.djvu/262

212 of physics. Both agreed that the direction of wave movement was from S. to N., with more or less of an eastern or western swerve from the magnetic meridian.

There was no material alteration, either in inclination or declination of the magnetometers noticed; but Professor Palmieri's views are, that every eruption of Vesuvius and Etna, and probably every earthquake, is accompanied by great electrical disturbance, which, he supposes, may affect the magnet. His seismometer at the Observatory upon Vesuvius was affected by the shock. The magnetic declination is very variable, both in short periods of time and for adjacent localities in and about Naples, and he thinks continually alters with the state of Vesuvius. I myself ascertained the declination in St. Lucia to be only 9° west in one spot; but blocks of lava used in building, pavement, &c., all more or less magnetic, make such observations very uncertain. The mean declination, however, for Naples, I obtained from the Observatory = 14° 30' west in February, 1858; and this agrees with the monthly printed determinations of the Royal Marine Observatory at Naples.

The whole of these five observers above mentioned agreed, that the shock at Naples was not attended with any noise whatever, either preceding, during, or succeeding the movement.

One gentleman only in Naples described to me sensations of sickness felt by him during the shock, which he first perceived while playing cards. In his case my impression was, that the affection was due to nervous excitement and alarm only. Conversation generally with persons of all classes in Naples, only tended to increase on my part the caution necessary in attempting to found any conclusion