by
them resembles that which would be caused by the passage of a rapid
succession of electric shocks, rather than any other I am acquainted
with.

GEOLOGICAL OBSERVATIONS AT ST. HELENA.

July 21.

After visiting Longwood and Napoleon's tomb we rode to Flagstaff Hill to
search for fossil shells. The whole soil that I saw was composed of
decomposed old volcanic rocks; but I saw no rock but basalt in different
stages of decomposition; sometimes it assumed the form of porphyry. I
also saw veins of quartz, gypsum, and jasper. On a part of Flagstaff Hill
there was a thin stratum of calcareous earth, in which shells are found.
My hip was so painful that I could not climb to the point where these
were, but an artillery soldier ascended and brought down some, and of
these I had several specimens given me; they are found associated with
bones which are apparently those of birds. None of these bones were given
to me but I saw and examined several specimens. The shells are very
numerous at this point.

On returning into town I found several specimens of dead land shells,
apparently recent; these lay on the sides of the hills, partly buried in
the soil, and bore the appearance of having been washed into this
position by the heavy rains.

July 22.

Rode over in the morning to Longwood, and then proceeded to Gregory's
Valley, lying between Longwood and The Barn. 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 appeara