seventeen metres.^ The rock of the 

 reef was found to have beneath it 

 beds of sands, shells, marls, and days. 

 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 H. Agnew, at 

 Parahyba do JSTorte, 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 

 consti'uction. Where the line crosses 

 the upper ends of three mangrove 

 swamps immediately northeast of 

 the city station, gi-eat 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 Melhoraraento dos portos do Brazil. 

 Relatorios de Sir John Hawkshaw. An- 

 nexes. Rio de Janeiro, 1875. 



Pk 



