This valley, nearly 1700 feet in depth, appears at one period to have been the scene of great volcanic disturbances.

The lowest rock I saw was a compact porphyritic one.

The upper strata of basalt were in a state of rapid decomposition; but the whole of the valley was traversed by basaltic dykes in every direction; these crossed one another in such a way that it was easy to tell their relative ages; for instance several of them were in the form of: So that one had been forced from its position by another long subsequently to its formation.
The general form of Gregory's Valley is a large basin bounded by a lofty precipitous mountain on one side called The Barn, and having a very narrow opening seaward, through which a small stream has cut its way.

A remarkable circumstance connected with the basaltic dykes is that they are composed of a more compact basaltic rock than the basalt which they penetrate, so that whilst the rock has mouldered away these basaltic dykes have remained standing; and, as in the progress of their decay they split up, they present the appearances of walls built by human hands, with regular layers of stones, and which traverse the ravines of the island in all directions.
As might be expected, I found regular basaltic crystals in this valley, and also a variety of quartz ore, and other crystals, in the veins traversing the basalt.

I also found the following remarkable section: This was in a side valley or ravine leading from Gregory's Valley in a southerly direction.
On going down to the sea I found many species of starfish.