ON THE CONSOLIDATED BEACH AT PERNAMBUCO, 239 
19. Nores on the Consotrpatep Beach at PrernamsBvuco. By J. CLARKE 
Hawxsuaw, Esq., M.A., F.G.8. (Read January 8, 1879.) 
THE narrow ridge of rock which forms the seaward protection of the 
harbour of Pernambuco, and which appears to be the remains of a 
consolidated beach laid bare by the slow upheaval of the coast, has 
become almost as well worn a subject of discussion as the parallel 
roads of Glen Roy. A drawing was given of it in a Dutch work* 
as early as 1624, and many travellers have since described and 
figured it in their works. It has been called a coral reef, and has 
been described as consisting probably of cretaceous rocks, and it 
was not until after Mr. Darwin had visited it in 1836 that its true 
nature was pointed out by him in a short account printed in the 
* London and Edinburgh Philosophical Magazine’ for 1841. 
The late Prof. Hartt, who has added so much to our knowledge of 
the coast of Brazil, confirms Mr. Darwin’s view as to the nature of 
the reef, and describes several similar formations at various points 
along the coast?. At Porto Seguro there is a consolidated beach 
very similar to that at Pernambuco ; there is also one at Santa Cruz. 
The stone reef shown on the chart at the mouth of the Rio Grande 
do Norte appears to be a consolidated beach, and patches of beach 
rock occur at other places; I saw some undermined by the sea along 
the rocky coast north of Bahia. 
In 1874 I examined the beach at Pernambuco; and in the course 
of some investigations made for Sir John Hawkshaw in the following 
year for a report to the Brazilian Government on the Port of Per- 
nambuco, a number of borings were made in the neighbourhood of 
the reef. Some of these passed through the reef itself, and they 
tend to complete our knowledge as to its extent laterally and beneath 
the surface. 
Section opposite the Marine Arsenal, Pernambuco, at right angles to the “ Reef.” 
(Horizontal scale, 1 inch = 500 feet. Vertical scale, 1 inch = 100 feet.) 
Arsencl Cnmy. 
Beds of Sund 2 Clay 
Difference between high and low water, ordinary spring-tides, 7-3 feet (2:27 metres). 
Briefly described, the consolidated beach (see fig.) consists of a 
ridge of sandstone from 25 to 75 yards broad, and, as shown by the 
borings, from 10 to 15 feet thick. The surface of the rock has a gentle 
slope towards the sea, the higher or landward edge being at the 
* ‘Reys-boeck van het Rycke Brasilien ;’ see ‘Geology and Physical Geography 
of Brazil, by O. F. Hartt p. 434. 
t J. pp. 188, 189, 232. 
