The first motion in the waters was their withdrawal, which was sufficient to completely uncover the bar at the mouth of the Tagus. At Cadiz, the first wave, which was the greatest, is said to have been sixty feet in height. Fortunately the devastating effect which this would have produced was partially warded off by cliffs.
At the time of the Jamaica earthquake (1692) the sea drew back for a distance of a mile.
In South America sea waves are common accompaniments of large earthquakes, and they are regarded with more fear than the actual earthquakes.
On October 28, 1724, Lima was destroyed, and on the evening of that day the sea rose in a wave eighty feet over Callao. Out of twenty-three ships in the harbour, nineteen were sunk, and four others were carried far inland. The first movement which is usually observed is a drawing back of the waters, and this is so well known to precede the inrush of large waves, that many of the inhabitants in South America have used it as a timely warning to escape towards the hills, and save themselves from the terrible reaction which, on more than one occasion, has so quickly followed.
At Caldera, near to Copiapo, on May 9, 1877, which was the time when Iquique was devastated, the first motion which was observed in the sea was that it silently drew back for over 200 feet, after which it rose as a wave over five feet high. At some places the water came in as waves from twenty to eighty feet in height.
At Talcahuano, on the coast of Chili, in 1835, there was a repetition of the phenomena which accompanied the destruction of Penco in 1730 and 1751. About forty minutes after the first shock, the sea suddenly retired. Soon afterwards, however, it returned in a wave twenty feet high, the reflex of which swept everything towards the sea. These phenomena were repeated three times.[75]
When Callao and Lima were destroyed, in 1746, the sea first drew back, then came in as waves, four or five minutes after the earthquake. Altogether, between October 28 and February 24, 451 shocks were counted. At one time the sea came in eighty feet above its usual level. One account says that the large waves came in forty-one and a half hours after the first shock, and seventeen and a half hours after comparative tranquillity had prevailed.[76]