OF SA>rT( ) DOMINaO. 



85 



again within a few miles to a more serpentinoid form, to reappeai as tlie same jasper 

 on the Jaina, and to again change, on the Upper Jaina and in nearly all the monn- 

 tains eastward, into a whitish rock, more or less talcoid and profusely stained with 

 iron. On the north side of the island the modifications of the shale are jnst as great. 

 The sandstones also undergo an equal number of variations, appearing of all colors 

 from black or dark gray sandrock to a white, granular quartzite. In shoi't, nearly 

 every color is represented; and naturally, all degrees of texture from the coarse 

 conglomerate of San Jose de las Matas, or Maniel, to the shale above described. In 

 one place only did I find siliceous segregations like the chalk flints, or more 

 probably, like the corniferous limestones of thel^ew York geologists. In the hill just 

 west of Bani the i-ock is a limestone, and in it are numerous streaks, lying in the 

 plane of stratification, of a light brownish limestone, very tough and breaking Avith 

 an irregular fracture. ISTear the base of the series, apparently, are strata of con- 

 glomerate, made up of pebbles very similar to those of the surrounding beds. These 

 pebbles seem to have been brought from long distances, since they are almost 

 invariably rounded by attrition. They are largest on the Upper Ocoa, near Maniel, 

 and on the north flat of the i-ange near San Jose de las Matas ; but at these points 

 they are rarely more than a few inches in diameter. I have endeavored in vain to 

 find the probable source of these pebbles. They are certainly not from the adjoining- 

 beds, although lithological researches were not wanting. They are not derived from 

 any deposit encountered by us on the Island, since the conglomerate strata extend 

 nearly, if not entirely, to the base of the stratified rocks. It is not probable that 

 further examination to the westward, in the yet unknown portions adjoining Hayti, 

 or lying within its borders, will develop their origin, since such a discovery would be 

 foretold by increase in the size and angularity of the pebbles in that direction. They 

 must therefore have been derived from some land then existing most probably to 

 the north or northwest of the present island, but now submerged or destroyed. The 

 conglomerate is variable in its character and the changes take place over com- 

 paratively limited areas. On the north side it is almost always cemented by a 

 coarse-grained red sand, the surfaces of the contained pebbles being stained by the 

 ferruginous nature of the matrix. This is the rule where the metamorphosis is not 

 very perfect. In one place, west of San Jose, the whole mass is rendered nearly 

 homogeneous in texture, the fracture crossing matrix and pebbles alike. In another, 

 on the Mao River, the whole is changed to a dark olive green, the coloring matter 

 having stained even the interior of the pebbles. On the Ocoa, some of the con- 

 glomerate is cemented by lime instead of sand, and in this case the pebbles are not 



A. p. S. — VOL. XV. V. 



