of the Amazons Valley. 61 



Of this section tlie following explanation is given : — 



" I. Coarse sands {sable grassier), forming the base of the drift 

 throughout, seen wherever the level of the water has uncovered the 

 lower beds of plastic clays. 



" II. The mottled plastic clay (argile plastique bigarree) shows 

 itself on a large scale along the sea-coast at Para, at the Island 

 of Marajo, Maranhao, and here and there in the hollows along 

 the course of the Amazons. 



" III. Laminated clay in very thin beds, with frequent indications of 

 cleavage. This deposit appears to be more considerable in the banks 

 along the course of the Rio Solimoes than in the lower part of the 

 Amazons. It is in these beds at Tonantins, on the Eio Solimoes, 

 that M. Agassiz has found leaves of dicotyledonous plants which 

 appear to be identical with species at present living in the valley of 

 the Amazons*. 



" IV. A crust of sandy clay, very hard, moulded in the inequali- 

 ties of the laminated clay. 



" v., VI., VII., VIII., & IX. Sandstone formation, — sometimes 

 regularly stratified and compact, especially in the lower beds (V.), 

 such as one sees on the borders of the igarapes-\ of Manaos ; some- 

 times cavernous and intermixed with irregular masses of clay (VI.), 

 especially well developed at Villa Bella and at Manaos ; at others 

 all the characters of a torrential stratification (VII., VIII., & IX.). 

 The deposits of this last nature arc only seen in the elevated hills of 

 Almeirim, Erere, and Cupati, and in the most elevated cliff's of the 

 borders of the river, as at Tonantins, Tabatinga, Sao Paulo, and on 

 the borders of the Rio Negro. 



" X. The argilo-arenaceous unstratified drift, occupying all the 

 inequalities of the soil resulting from the denudation of the sand- 

 stone with toiTential stratification. It is in this drift that MM. 

 Agassiz and Coutinho have found true erratic blocks of diorite, a 

 metre in diameter, at Erere. This formation is never met with on 

 the cliffs elevated several hundreds of feet in height. There is not a 

 trace of it on the summit of the hills of Erere." 



" The fact that the coarse sand No. I. appears throughout 

 at the level of low water, that it follows the general slope of 

 the valley, shows incontestably that the deposition of this 



* " These leaves occur in a fine, soft, grey clay, resembling very closely 

 the recent alluvial clays of Brazilian rivers ; they are excellently pre- 

 served. The leaf is partly carbonized ; but it curls up from the surface on 

 drying, and may be detached, leaving a beautiful impression of the vena- 

 tion &c. (Ch. F. Hartt.)" 



Sir Charles Lyell (Principles, vol. i. p. 4G6) speaks of these leaves as 

 being found in bed XL, in the delta of the Amazons on the island of 

 Marajo, whereas they really occur in Bed III., and more than 2200 miles 

 up the Amazons. 



t The Indian name for small streams; literally, "canoe-path," from 

 igara, a canoe, and pes, a path. 



