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TIIE M O CA-SSTQUIAKi:.
traversed. T h e s e veins are several inches broad, and their masses proved that their date a n d formation are very different. I saw distinctly that, wherever they crossed each o t h e r , the veins containing mica and black schorl traversed and drove o u t o f their direction those which contained o n l y white quartz and feldspar. A c c o r d i n g t o t h e theory of W e r n e r , t h e black veins w e r e consequently o f a more recent formation than the white. B e i n g a disciple o f t h e school of F r e y b e r g , I could n o t b u t pause with satisfaction at t h e rock o f U i n u m a n e , t o observe the same p h e n o m e n a near t h e equator, which I had so often seen i n t h e mountains o f m y own country. I confess that the t h e o r y which considers veins as clefts filled from above with various substances, pleases me somewhat less now than it did at that p e r i o d ; but these m o d e s o f intersection and driving aside, observed in the stony and metallic veins, d o n o t the less merit t h e attention o f travellers as being o n e o f the most general and constant o f geological p h e n o m e n a . On t h e east o f Javita, all along t h e Cassiquiare, and particularly in the mountains o f D u i d a , t h e n u m b e r o f veins i n t h e granite increases. T h e s e veins are full o f holes and druses; a n d their frequency seems t o indicate that t h e granite o f these countries is n o t o f very ancient formation. W e f o u n d some lichens o n t h e r o c k U i n u m a n e , opposite the island o f Chamanare, at t h e e d g e o f t h e r a p i d s ; and as the Cassiquiare near its m o u t h turns abruptly from east t o south-west, we saw for the first time this majestic branch o f the O r i n o c o in all its breadth. I t m u c h resembles the K i o N e g r o in t h e general aspect o f the l a n d s c a p e .
T h e trees o f
the forest, as i n the basin o f the latter river, advance as far as the beach, and there form a thick c o p p i c e ;
but the Cassi-
quiare has white waters, a n d m o r e frequently changes its direction. Its breadth, near t h e rapids of Uinumane, almost surpasses that o f the Rio N e g r o . I found it everywhere from t w o hundred a n d fifty t o t w o hundred and eighty toises, as far as above Vasiva. Before we passed t h e island o f Garigave, we perceived t o t h e north-east, a l m o s t at the horizon, a little hill with a hemispheric summit ; the form which in every zone characterises mountains o f granite. Continually surrounded by vast plains, the solitary rocks and hills excite the attention o f the traveller. Contiguous