BRANNER: THE STONE REEFS OF BRAZIL, 35 
He notes that a soft conglomerate is found in the bottom of the harbor 
behind the reef, 
Borings were made on the reef showing the rock to be not much more 
than a metre thick. It is said that there was formed a channel between 
the reef and the shore. 
The stone reef at Rio Grande do Norte. — The immediate shores about 
the mouth of the Rio Grande do Norte are covered far and wide with 
shifting sands. Southeast of the city these sands are being blown 
over the hills and into the river to such an extent as to threaten to 
destroy the navigability of the stream between the city of Natal and the 
bar. Behind these dunes mangrove swamps spread out across the mud 
flats that follow the river as far up as the tides are felt. 
The topography of the region is beautifully seen from kilometre 8 of the 
Natal a Nova Cruz Railway. From this point one looks down upon a 
broad flat valley where water merges into mangrove swamp and swamp 
into flat dry lands, all ending abruptly against the sedimentary hills to 
the north. This flat country continues westward up the estuary of the 
Jundiahy to the town of Macahyba, everywhere .the same as far as the 
general features are concerned. 
In the city of Natal itself the same topographic relations are visible 
in the open square in front of the railway station. 
Fria. 12. Section from Natal to the Stone Reef. 
It is worthy of note that the reef is on a level with the mangrove 
Swamps, and but slightly below the level of the land upon which the 
lower city stands. The Tertiary hills on which the upper part of the 
city stands plunge as abruptly beneath the flat land at their base as if 
that land were a water surface. 
The Natal or Rio Grande do Norte stone reef connects with the shore 
at its southern end, while its northern end stands squarely across the 
mouth of the Potenguí, or Rio Grande, во that the water of that stream 
flows round the north end of the reef to escape to the sea. The length 
of the reef from its northern end at the bar to where it joins the land 
is fifteen hundred metres ; its length from where it joins the land to its 
southern extremity is three kilometres, making a total length of four 
