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BRANNER: THE STONE REEFS OF BRAZIL. 99 
effectiveness is due to the coral reef that lies outside, however, and 
greatly reduces the force of the surf that reaches it. At its southern end 
it is split in two. South of this end and in a general line of the main reef 
are five or six isolated rocks that are probably remnants of the reef in 
that direction. North of the north end of the reef there is no flat land 
on the beach, the cliffs coming close up to the water. There are no rocks 
on the beach as shown on the hydrographic charts. 
The reef has the appearance of having been nearly everywhere more 
or less cracked and these cracks filled with sand which is now hard like 
the rest of the rock. In places the cracks have been washed open to a 
depth of more than half a metre. Tho cracks run in every direction, 
but the greater part of them are parallel with the reef. Along the sides 
blocks from three to six metres long and from one to four metres across 
have broken away from the main reefs on both sides and have sunk into 
the sand and mud next to the reef. In some places the reef rock over- 
hangs on the landward side where it seems to be undercut by the stream 
or outflowing tide. 
North of the river the old town of Porto Seguro stands upon a plateau 
forty-five metres high, and for the most part covered with forest. 
The following description of this reef is given by Hartt, who examined 
it in 1865:1 “The rock is obliquely laminated as in a sand beach, the 
lamina dipping seawards at a small angle. It is composed of" rather 
fine sand, with occasional small pebbles, compactly held together by a 
calcareous cement. It contains an abundance of recent shells, Venus, 
Cerithium, Chama, etc., such as now live on the sea beaches of the 
vicinity.” 
There is, however, a marked difference between the rock of this reef 
and that of the others. The sand is much whiter and, on the average, 
coarser, Many of the pebbles are as large as pigeon’s eggs, and the 
fossil shells are moderately abundant. In one block I found a piece of 
the coral Porites embedded in the reef rock. In places the reef rock is 
exceedingly hard and breaks through the quartz grains with an almost 
glassy fracture. 
My general impression of the Porto Seguro reef is that it is one of 
the weakest of the Brazilian stone reefs, It is an important one because 
it protects the port in the great Cabral Bay already partly protected 
by the great coral reefs outside. 
Notes upon little-known stone reefs. — The preceding detailed descrip- 
tions of individual stone reefs contain all the notes made upon the reefs 
1 Geology and physical geography of Brazil, p. 229. 
