192 



ON THE TOrOGEAPHY AND GEOLOGY 



the extreme point of Latoma hill, covering the tract known as Yerba Buena. This 

 is an outlier of Loma Gristina, and strikes about north and south, dipping west 25°. 



J^ear the summit of Pomiel are numerous caves in the limestone, some of them 

 of considerable extent. The one most visited consists of a succession of chambers, 

 perhaps 200 yards or more in length. Its floor is nearly level and is covered with 

 little or no deposit of any kind. Adjoining it is another of nearly equal extent, in-» 

 habited by myriads of bats, very few of which are found in the first. Their dung 

 forms a layer over the floor varying from a few inches to several feet in depth, mixed 

 only with a few elytra of insects on which they feed. Other caves, but smaller than 

 these, occur in Calaboso. At Latoma is a beautiful spring welling out from the base 

 of a limestone bluft", probably through a similar cave. The water of the Nigua for a 

 mile or two above this hill disappears under the sand of the river bed, and doubtless, 

 on reaching the limestone percolates through fissures to find vent finally at this point. 

 The quantity of water issuing here is about equivalent to that in the river bed at 

 Tablasas. 



A little Miocene Tertiary is found above this spring on the south flank of Pomiel, 

 more occurs on Calaboso, but the whole of Loma Gristina is made up of beds of 

 conglomerate, sandstone and calcareous claystone. The dip varies at low angles 

 from west to south ; the most prevalent being about 15° southwest. The base of this 

 deposit is everywhere a coarse conglomerate covered by sandstone while the earthy 

 and calcareous beds form the upper part. I found but few fossils and these in very 

 imperfect condition but sufficient to prove the synchronism of this with the rocks of 

 the Gibao Yalley. ^ . . . • . 



In the flat land south of Galaboso and just east of San Cristobal, one or two very 

 -small outcrops of the conglomei-ate occurs, and over these are beds of coast limestone 

 which extend to the sea. In one spot I found the phenomenon of coast limestone so 

 full of pebbles as to form a true conglomerate, and with pieces of branched corals, not 

 water-worn, mingled with the stones. But the explanation of the circumstance ex- 

 hibits itself in a bed of Miocene conglomerate, underlying the limestone in an adjoin- 

 ing little hill side. The pebbles were washed out of one formation to be immediately 

 re-imbedded in the other. While the Isabella, Jaina, ]Nizao, and other streams brought 

 down lai-ge deposits of gravel during the Post Pliocene period, the quantity carried 

 seaward by the Nigua must have been very small. All of these rivers deposited their 

 loads at and east of their mouths. But east of the mouth of the J^igua, the gravel 

 mass is very inconsiderable, both in area and thickness, and the limestones come up 

 almost to the ancient coast line. It was probably then, as now, a nearly dry stream. 



