seventeen metres." The rock of the 
reef was found to have beneath it 
beds of sands, shells, marls, and clays. 
Some of the clay beds are more than 
two metres thick. These clays afford 
additional evidence of the outbuild- 
ing by silts of the formerly indented 
coast-line. Clays being light, sedi- 
ments can be deposited only far 
enough offshore to be out of the 
reach of the strong in-shore waves. 
The beach at the time of the depo- 
sition of the clays must therefore 
have been further inland, and the 
clay beds were buried by later sedi- 
ments swept seaward as the beach 
was built outwards. 
‚Evidence of buried rock-channels. 
— Somewhat in the same line is the 
evidence of a buried channel discov- 
ered by Mr. Samuel Н. Agnew, at 
Parahyba do Norte, on the line of 
the Conde d'Eu railway. In 1887-8 
this railway was prolonged from the 
city of Parahyba to Cabedello, at 
the mouth of the Parahyba river, 
and Mr. Agnew had charge of the 
construction. Where the line crosses 
the upper ends of three mangrove 
swamps immediately northeast of 
the city station, great difficulty 
was experienced in carrying the 
road-bed over the soft mud, owing 
to its yielding under pressure and 
allowing the railway to sink. In- 
asmuch as the largest of these 
mangues has rock cuts on both 
sides of it, it was assumed that the 
mangues had rock bottoms, and 
accordingly soundings were made 
1 Melhoramento dos portos do Brazil. 
Relatorios de Sir John Hawkshaw. An- 
nexos. Rio de Janeiro, 1875. 
17 Kivomerers 
El 
Karlway 
ом THE CONDE 0" Eu RAILWAY SHOWING THE DEPTH OF THE MUD FILLING SUBMERGED TRENCHES IN LIMESTONE 
Section 
a CRETACEOUS LIMESTONE 
Мир OF MANGROVE SWAMPS 
METERS 
METERS 
200 
—— 
° 109 
912345 p 
PE, 
VERTICAL 
HORIZONTAL 
SCALE { 
Fic. 81. 
