BRANNER: THE STONE REEFS OF BRAZIL. 49 
barely large enough for jangadas to pass through. The breaks are 
most abundant south of Mamanguape Point where the outflowing river 
strikes it, Several of the minor breaks, even at the lowest tides, have 
the water flowing through them between and beneath the loose blocks 
that fill them. 
Strictly Speaking, the reef as a whole is not straight, but neither is it 
very crooked. The bends in it are quite apparent when one sees the 
reef itself, but on a map of small scale they hardly appear. These 
curves are such as one may see on any approximately straight beach. 
Considered in cross-section, the surface as seen from the bar has a 
gentle slope seaward. In most places the landward face is abrupt, and 
the channel of the Mamanguape River passes close up against the reef- 
wall. Toward the southern end, however, and especially where the 
inner face has been protected by the secondary reef, the profile comes 
down at a gentler angle or by a series of small steps or low terraces. 
Fig. 20. Section across the Mamanguape stone reef. 
The outer edge of the reef is here and there broken off with beauti- 
fully smooth vertical faces. But even in such cases it is protected to a 
great extent by its own fragments, many or most of which are gigantic 
blocks undermined on the seaward side and let down to where they now 
lie. То a notable extent these blocks lie at angles that make them most 
effective protective agents for the rest of the reef, and least liable to in- 
Jury themselves from the onslaught of the sea. The following examples 
(Fig. 21) are types of the fractures observed on these faces. 
Tn all these cases the sea is to the right and the reef to the left. It 
is noticeable in these instances that the broken fragments have the 
appearance of having been let down by undermining, and they now lie 
80 as to serve as effective protection to the remainder of the reef, 
whether from undermining or surface wear. Many cases were observed, 
however, in which the fragments lie altogether at haphazard, 
Some sheer faces more than three metres high are openly exposed to 
а tremendous surf apparently without being in the least affected by it. 
At one place there is such a face sixty-five metres in length. Now and 
then one may observe, when the surf is powerful, that the shock or jar 
of the blows is very marked over a given area, I take it that these 
VOL, XLIV, 4 
