Within historical times no signs of volcanic activity have, I believe, been manifested in any part of St.Jago.Even the form of a crater can but rarely be discovered on the summits of the many red cindery hills; yet the more recent streams can be distinguished on the coast, forming lines of cliffs of less height, but stretching out in advance of those belonging to an older series: the height of the cliffs thus affording a rude measure of the age of the streams.
During our stay, I observed the habits of some marine animals.

A large Aplysia is very common.

This sea-slug is about five inches long; and is of a dirty yellowish colour, veined with purple.

On each side of the lower surface, or foot, there is a broad membrane, which appears sometimes to act as a ventilator, in causing a current of water to flow over the dorsal branchiae or lungs.

It feeds on the delicate seaweeds which grow among the stones in muddy and shallow water; and I found in its stomach several small pebbles, as in the gizzard of a bird.