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blende, which we had found at Javita, and 

 which assumes a syenitic aspect. We leftMan- 

 davaca at half after two in the morning. We 

 had still to struggle during eight days against the 

 currents of the Cassiquiare; and the country, 

 through which we had to pass in order again to 

 reach San Fernando de Atabapo, is so desert, 

 that we could only hope after a passage of thir- 

 teen days, to find another Observantin mission, 

 that of Santo Barbara. After six hours' voyage, 

 we passed on the east the mouth of the Idapa, or 

 Siapa, which rises on the mountain of Unturan, 

 and furnishes near it's sources a portage to the 

 Rio Mavaca, one of the tributary streams of the 

 Oroonoko. This river has white waters, and 

 is not more than half as broad as the Pacimoni, 

 the waters of which are black. It's upper course 

 is strangely disfigured on the maps of La Cruz 

 and Surville, which have served as models 

 to all subsequent maps. I shall have occa- 

 sion to mention the hypotheses, that have 

 given rise to these errors, in speaking of 

 the origin of the Oroonoko. If father Caul in 

 could have seen the map, which has been pre- 

 fixed to his work, he would have been surprised 

 to find fictions reproduced in it, which he has 

 himself combated by accurate ideas acquired on 

 the spot. This missionary simply says, that the 

 Idapa rises in a mountainous country, near 

 which live the Amuisana Indians. These In- 



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