PHYSICAL HISTORf OF THE AMAZONS. 413 



blue, and also black and white. It is from these beds that 

 the Indians prepare their paints. These clay deposits as- 

 sume occasionally a peculiar appearance, and one which 

 might mislead the observer as to their true nature. When 

 their surface has been long exposed to the action of the 

 atmosphere and to the heat of the burning sun, they look 

 so much like clay-slates of the oldest geological epochs that, 

 at first sight, I took them for primary slates, my attention 

 being attracted to them by a regular cleavage as distinct as 

 that of the most ancient clay-slates. And yet at Tonantins, 

 on the banks of the Solimoens, in a locality where their 

 exposed surfaces had this primordial appearance, I found in 

 these very beds a considerable amount of well-preserved 

 leaves, the character of which proves their recent origin. 

 These leaves do not even indicate as ancient a period as the 

 Tertiaries, but resemble so closely the vegetation of to-day 

 that I have no doubt, when examined by competent author- 

 ity, they will be identified with living plants. The pres- 

 ence of such an extensive clay formation, stretching over a 

 surface of more than three thousand miles in length and 

 about seven hundred in breadth, is not easily explained 

 under any ordinary circumstances. The fact that it is so 

 thoroughly laminated shows that, in the basin in which it 

 was formed, the waters must have been unusually quiet, 

 containing identical materials throughout, and that these 

 materials must have been deposited over the whole bottom 

 in the same way. It is usually separated from the superin- 

 cumbent beds by a glazed crust of hard, compact sandstone, 

 almost resembling a ferruginous quartzite. 



Upon this follow beds of sand and sandstone, varying in 

 the regularity of their strata, reddish in color, often highly 

 ferruginous, and more or less nodulous or porous. They 



