200 W. M. Gabb—Notes on Cosia Rica Geology. 
Two large rivers drain the region. These are the Tiliri 
is likely to remain so, until some traveller more adventurous 
than any yet found dares to penetrate the region. The Indians 
reported the country to be almost impassable, and say it 
never seen a granitic dike. The material seems to have beet 
forced up from below in a plastic state, sufficiently heated to 
have changed the character of the overlying rock wherever It 
came in contact with it, but never sufficiently fluid to penetrate 
any possible fissures that may have existed. True granite 
rarely occurs, while syenites are much more comm 
he = 
on. 
rock is almost always rather fine-grained, and while hornblende 
abounds, mica is rather the exception than the rule. The roe 
is lighter in color, and of a slightly coarser grain at the more 
eastern exposures than farther west. I saw nowhere the slight- 
est approach to a gneissoid structure, or any other sign that 
ic origi 
would indicate a metamorphic 
facts point to its having been quite recently in a heated co 
