of the Amazons Valley. 63 



mense amount, and a very wide strip of Tertiary rocks has 

 been removed. I believe that these deposits once extended 

 beyond the Abrolhos, and that south of Cape Roque the sea 

 has cut them away for a mean width of fifty miles or more." 



Prof. Hartt adds': — " At first I was disposed to regard the 

 Brazilian formation in question as Triassic ; but I soon found 

 that it was underlain unconformably by Cretaceous rocks in 

 Bahia, and I came to the only conclusion possible — that it 

 was older than the Drift, and newer than the Cretaceous. I 

 can see no reason, therefore, for considering the coast beds 

 any thing l^ut Tertiary, though they may be, and probably are, 

 very late Tertiary. It has seemed to me that the fact of the 

 occurrence on an open sea-coast of clays and sandstones pre- 

 cisely similar to those occupying the lower plains of the Ama- 

 zons, as at Pard,, and in fact tying in with them, relieves one 

 of the necessity of looking to a freshwater origin for the 

 Amazonian beds." 



These observations (coming as they do from one of Prof. 

 Agassiz's own travelling companions and the geologist of the 

 expedition, who has extended his knowledge of the geology 

 of the district by a subsequent visit to Brazil) are of consider- 

 able importance. Whilst differing, however, from his chief 

 as to the age and origin of these Amazonian beds, Prof. Hartt, 

 like Agassiz, is a firm believer in the doctrine of " glaciers 

 under the tropics down to the present level of the sea." 



The only reason adduced by Prof. Agassiz for not regarding 

 these formations as marine is the negative one, that he found 

 no marine fossils in them. On the other hand, the only posi- 

 tive evidence which he seems to have found in proof of the 

 freshwater origin of this vast deposit is the occurrence of di- 

 cotyledonous leaves in a single locality on the Hio Solimoes, 

 more than 2000 miles up the river. 



The occuiTcnce of erratic blocks of diorite " a metre in dia- 

 meter " in the unstratified drift X. is adduced as indubitable 

 proof of glacial agency ; but the transporting-power of a river 

 like the Amazons (several miles in breadth), swollen by rains 

 and melted snows, may probably have sufficed. Or, as they 

 occur elsewhere besides in the valley itself, they may quite as 

 reasonably have been brought from the Antarctic by icebergs 

 and dropped during the submergence of the eastern ])rovinces. 



On the 7th October, Prof. James Orton, of Vassor College, 

 Poughkeepsie, New York, addressed a letter to the 'Geological 

 Magazine ' announcing that, in his late expedition across the 

 continent, he had discovered a fossiliferous deposit at Pabos, 

 and also that liis correspondent Mr. Hauxwell, at his sugges- 



