This phenomenon was observed on the 5th July and three following days. It did not occur on all parts of the coasts of Great Britain. In England, it was observed only on the south shores of Cornwall and Devonshire. In Scotland, it was observed on the east coast; and there it was seen at a great many places, between Eyemouth in Berwickshire and the Shetland Islands.

It was only on the 5th July that the oscillation occurred on the Cornish and Devonshire coasts. It prevailed on the Scottish coast, however, from the 5th to the 7th July inclusive.

The phenomenon consisted of a flux and reflux of the sea, beyond what could be accounted for by ordinary tides, or any wind prevailing at the time. The water suddenly rose up and sunk down from 2 to 5 feet in perpendicular height, producing effects more or less striking, according to the shelving character of the shore.