BEACH AT PERNAMBUCO. 241 
sents a very remarkable appearance when seen at the time of low 
water. The whole of the surface between high- and low-water 
mark is scored by a series of grooves parallel to the direction of the 
groyne and transverse to the shore-line. The shore is bare of shingle; 
but pebbles are to be found here and there along the bottom of the 
grooves, and there is a sprinkling of shingle about a yard in width 
along the side of the groyne and along the base of the cliff. The 
grooves on the higher part of the foreshore are from 2 to 24 feet 
deep and about a foot wide ; but lower down the foreshore they soon 
diminish in size, and do not vary much over the greater part of it, 
being from 4 to 5 inches wide, and from 4 to 8 inches deep. They 
are narrower towards the bottom, which is rounded and hollowed 
out more in some parts than in others. They branch into one 
another in places like those at Pernambuco. Though they are 
generally only a few inches apart, occasionally there is a greater 
width of chalk between them; and this is generally marked by an 
incipient groove a foot or two long with rounded ends, as if a piece 
of chalk had been irregularly scooped out with a gouge. ‘The 
grooves diminish in number eastward of the groyne; and I have 
not noticed a similar appearance of the foreshore elsewhere, though 
grooves occur all along the foreshore, but at rare intervals, and are 
caused in many cases, I fancy, as much by the flow of land-water 
from the base of the cliff as by the action of the waves on the 
shingle. I can only attribute the presence of the grooves in such 
numbers at the above place to the regular action of the wash of the 
sea on a small supply of shingle, the groyne acting as a guide to the 
wayes, and also intercepting the west to east drift which prevails 
along the coast. 
It will be seen from the borings made at Pernambuco that there 
is another layer of rock about 8 or 9 feet vertically below the present 
ridge (see fig. p. 239). This rock was met with in two of the borings 
through the reef at depths of 13 and 16 feet below low water of 
spring-tides. Rock is again met with in the same line, and at a 
depth of from 16 to 19 feet below low-water spring-tides, at the 
Barra Grande, about a mile to the north of the lighthouse, which is 
built on the northern end of the reef. Rock was not met with else- 
where in any of the borings made in the neighbourhood of the reef*. 
It would therefore appear possible that there is another ridge of 
rock running at a lower level on the line of the existing reef. Can 
this be a consolidated beach of older date? ‘The difficulty in the 
way of such a conclusion is that it would imply a recent depression 
in the level of the land, of which, I believe, there is no other evi- 
dence. Onthe contrary there are conclusive signs that the coast has 
recently risen in level, and that the southern part of the continent has 
been slowly rising for a long period of time. It would be remarkable, 
* One other boring, made in deep water near the reef, touched on rock near 
the surface; but as no rock was met with in another boring made near the 
same place, the rock met with in the first instance was probably a block detached 
from the reef, 
