or 
TRANSACTIONS OF THE SECTIONS. 71, 
specimens of the Equiseta occur, a circumstance which, together with the absence of 
branches or larger twigs, and the full extension of the largest palmated leaves, seems 
to indicate that the vegetable remains had been accumulated in a marsh or shallow 
water, when overflowed by the volcanic matter. 
On Recent Changes of Sea-level. By Rozerr Austen, F.R.S. 
In the present state of our knowledge, it is no longer sufficient to refer all changes 
of level, of apparently recent date, to the general head of “Raised Marine Beds or 
Beaches,” inasmuch as many phznomena, which were originally so classed, are now 
known to be referable to distinct periods of time. Yet, though thus much has been 
ascertained, we have not hitherto been informed as to what may have been the 
exact nature and amount of oscillation recorded at any one particular spot; and it 
is only by observations to be made at, or on, the same vertical line, that this ques- 
tion can be conclusively settled ; for such recent changes having taken place since 
the marine fauna was such as it is at present, its remains afford no assistance ; and 
different levels, if observed at separate places, may possibly, on the assumption of 
unequal movements, belong to the same period. My object therefore in the present 
short communication, is to describe some sections which I have recently had an op- 
portunity of observing on the south coast of Cornwall, whereby to define the order 
of some recent changes. It is only under certain conditions that the evidence in 
questicn is clearly presented, the oscillation having been of small amount ; all traces 
of former lower levels of the land have disappeared along the whole line of the 
yielding strata of our southern shores ; and along the greater part of the line of 
transition slates, the planes of bedding or cleavage, dipping at high angles south- 
wards into deep water, offer but a few spots for the accumulation of beaches; the 
favourable conditions seem to be such as are presented by such situations as the 
as west of Falmouth Harbour, and which may be taken as an illustration of 
them all. 
Φ The slate strata at this place are nearly vertical, and are composed of beds of un- 
equal hardness, so that the action of the sea on their edges wears them out into a 
serrated surface of troughs and sharp ridges, from high-water mark to some depth 
below; at which depth is the usual accumulation of coast sand and shingle. 
The rise of the tides at the spot in question is about 18 feet, and the lines which 
the coast presents at low water are,—Ist, that which defines the upper limit of Fucus 
vesiculosus, which everywhere clothes the rocks in thick masses; and 2nd, a line 
defining a zone parallel with the former, presenting a perfectly clean surface of rock, 
and which represents the highest reach of cvast waves, and along which their full 
power is exerted: the troughs of this zone are occasionally occupied by sand and 
large rolled blocks; these two zones are to be seen at places as far as the eye can 
reach, bearing a constant relation to the present sea level, and everywhere present- 
ing a like character as to the form in which its surface is abraded: from the upper 
zone commences the rise, more’or less steep, of the cliffs or wall of coast line. 
At the place in question, however, a still higher zone is to be observed, and the 
foregoing detail has been required, inasmuch as this zone, in all its features, is an 
exact counterpart of the upper portion of the lower one, and must have been formed 
when the action of the line of breakers reached such level. This zone consists of 
bare rock, but the surface of the slates, instead of being clean, is covered with a 
growth of gray and orange lichens; whilst in the clefts and troughs are masses of 
séa-pink (Armeria maritima), Plantago maritima, and grasses. ‘This zone is now 
constantly beyond the reach of the sea. At its upper limit, rises a vertical cliff of 
variable height, which must have been produced when the sea-level reached its base. 
We have in this zone a clear indication of a change of level; the most recent, so 
far as elevation is concerned, which we find recorded, and the amount of which has 
not exceeded, or may be equal to half the present interval between high and low 
water. 
The line of vertical cliff which here and in other places overhangs this raised 
marginal sea zone, consists of an accumulation of variable, but often of great thick- 
ness, on the nature and origin of which we need not now enter ; but at its base, and 
extending inland beneath it, are marine beds of sand and shingle, corresponding. 
