344 '^Jic American Geologist. Doc.imVxn-, i899 
part of the reef. This unusual widtli seems to be due to 
the union at this point of the inner and outer ones. From 
the fort the northern end of the inner reef appears to branch 
off somewhat from the outer one, and then disappears. On 
the opposite side of the river channel are some rocks which 
we did not ourselves examine, but they lie in the axis of this 
inner reef which fact leads me to infer that they are a part 
of this reef. A government engineer who at one time had 
charge of the port improvements at Natal stated ^o the sen- 
ior author that these rocks were sandstones and were of the 
same character as the rocks of the reefs. Toward the south 
end of the main reef this secondary or inner one first shows 
about 1800 feet south of the fort. It is parallel with the out- 
er reef and from 275 feet to 325 feet to the landward of it 
for about two-thirds of a mile. It is onl}' from 30 feet to 
100 feet wide, is composed of the same rock as the great 
reef, and is thickly coated with corallines and barnacles. 
At high tide this reef is covered b}' the water of the lagoon 
between the reef and the land. At its highest point it is 
only three feet above the sand flat about it, and at hige tide 
it is a foot or more under it. 
The land immediately back of these reefs is rather low, 
but near the coast is made up chiefly of sand dunes. Behind 
or to the landward of these dunes are extensive tide marshes 
covered with mangrove.s. Only at their extreme southern 
end do they approach one of the high red bluffs so charact- 
eristic of the northeast coast of Brazil. 
When we went to Rio Grande do Norte it was in the ex- 
pectation that we should be able to photograph the reefs 
from the lighthouse, for views taken from that position 
would give a better idea of the form and character of th.e 
reefs than maps and verbal descriptions. This photograph- 
ing was, most unfortunately, not permitted. 
The subjects of the origin and history of the stone and 
other reefs of northeast Brazil will be treated later and at 
length b}' the senior author. 
Natal, Rio Grande do Norte, July 2, i8gg. 
