BRANNER: THE STONE REEFS OF BRAZIL, 85 
sound. The surface of the Rio Formoso reef, howe 
whole, as ragged and rough as those of m 
reefs. 
The broken stone generally shows 
pebbles and shells. The pebbles 
ver, is not, on the 
any other of the stone 
quartz sand mixed with some 
are also of quartz, and the shells are 
of bivalves, gasteropods, etc., such as live at present along the coast in 
the vicinity. The shells most abundant are the prettily colored bivalves 
Venus, popularly known here as mariscos. 
In many places, in fact, in almost all parts of the reef, cr 
to have been formed and then to ha 
that has hardened like the rest of the 
the same direction аз the reef, but 
angles, and at other times diagonally. In two places the reef has small 
breaks nearly or quite through it, crossing diagonally, and with the 
appearance of being due largely to the presence of the cracks, 
From the land end on the south outward there is no break of impor- 
tance until about halfway the whole length of the reef 
› Where there 18 
a baretta ог passage for canoes and Jangadas. This break is known as 
the barreta das Jangadas. It is here that the reef receives the full 
force of the ebbing tide as it comes down from the river. From the 
barreta das Jangadas to the outer end, the side facing the river is 
either perpendicular or overhanging. In the barreta itself the rocks in 
the bottom of the Passage are hard and appear to be the same as those 
I suppose the rocks in the 
age to have formerly stood even with the surface of 
the reef, but being undermined by the strong sand-laden currents, they 
have lost their support and fallen where they now lie. These blocks, or 
more properly slabs, are all large and broad, and of the same average 
thickness as the harder upper part of the general body of the reef. 
From this place to the outer end, five hundred an 
there are two other breaks, both of them sm 
than this one, 
acks appear 
ve been filled up again with sand 
reef. These cracks have generally 
they sometimes crosg it at right 
d seventy metres, 
aller and of legs importance 
The whole of the riverward face of the reef 18 
broken away where left without support 
very | 
undercut. Blocks have 
„and in one place especially, 
arge pieces have fallen, and, with one end held fast by the sand 
and mud of the bottom of the channel, remain with the other end 
tilted high in the air. One of these is so high that it is not covered 
even by the highest tides ; this one is popularly known hereabout as the 
Pedra de Nossa Senhora, or the Rock of Our Lady. 
At still another place the reef is entirely undermined, while the sur- 
