146 BULLETIN : MUSEUM OF COMPARATIVE ZOOLOGY. 



along the line of the road to ascertain the depth of the mud down to 

 the Tock floor. These soundings were taken Avith steel rods, and the 

 mud was so soft that two or three of the rods were lost by slipping from 

 the hands of -the men and disappearing very much as if they had fallen 

 into water. The original profile of the railway, together with rock cuts 

 and soundings across these mangues, was kindly furnished me by ^Ir. 

 Agnew. They are copied here, beginning with the upper left hand at 

 kilometre 16 from Cabedello. 



It will be seen that the mangrove swamp here fills gullies tliat were 

 cut originally in the hard limestone. The outlines show them to have 

 the form common to stream channels, and as such channels could only 

 be cut when the place was above water level, we are obliged to assume 

 that the land at this place formerly stood enough higher to allow water 

 to flow freely down these gullies. The greatest depth of the mud along 

 the profiles is 11.70 metres, which, added to the depth of water in the 

 mangue above the mud, gives a total depth of at least 12 metres. In 

 order to restore the conditions under wliicli this deepest channel was 

 cut, we must assume an elevation of the land of at least twelve metres. 

 But inasmuch as the railway runs across only tlie upper or shallower 

 ends of these swamps near the Parahyba hills, it is fair to assume that 

 the main channel of the Parahyba is considerably deeper. Their prox- 

 imity to the hills likewise precludes the possibility of the channels 

 having been cut by tidal scour. 



Additional views of depression. — Shaler expresses the opinion, prob- 

 ably based upon sucli maps of South America as are available, that the 

 region about the mouth of the Amazon "has recently been lowered to a 

 considerable depth." ^ 



Dr. James Geikie says : " The general trend of the coast-line of South 

 America . . . from Pernambuco to the mouth of the river Plate, coin- 

 cides with the direction of the continental plateau, and may be said, 

 therefore, to have been determined by crustal movements."^ He thinks 

 the region about Rio has been depressed. 



Although Hartt expressed a belief in a recent elevation of the coast, 

 he also refers to evidence of a recent depression. This evidence consists 

 of recent cemented sands covering " drift " clays " down nearly to low 

 tide. This fact seems to prove satisfactorily that formerly the land 

 stood at a higher level even than now." ^ 



1 N. S. Shaler. Evidences as to change of sea-leveL BuU. Geol. Soc. Amer., 

 1895, \1., p. 162. 



2 James Geikie. Earth sculpture. New York, 1899, p. 332. 



3 Geology and physical geography of Brazil, p. 572. 



