W. M. Oabh on the Geohgy of Santa Dommgo. 255 



trated by a map and several sections. I do so because the 

 above description is totally at variance with the article quo- 

 ted, and these examinations were made with a fall knowledge 

 of the statements of Mr. Heneken. I make this explanation, 

 not from any feeling of antagonism, and may mention that the 

 author died several years ago on this island ; but a regard for 

 truth requires me to state that the descriptions there given of 

 the geology of the Cibao are, at least, very extraordinary. 

 Among other things, he has taken a part of the Tertiary sand- 

 stones, erected them into an older formation, and states, incor- 

 rectly, that it underlies unconformably the blue fossiliferous 

 shales. Another important inaccuracy is his assertion that the 

 north range, at Mt. Maraso, is an anticlinal of older rocks (see 



north of the summit of the mountains. The errors arose with- 

 out doubt from the inexperience of the observer. 



Bordering almost the entire coast, from Manzanilla bay, 

 around the eastern end of the island to the north of the Nizao 

 nver, on the south side, is a deposit of horizontal limestone of 

 very modem origin, in places full of living corals and very 

 imperfect casts of living species of mollusca, but more usually, 

 where not hardened by the weather, a white or cream-colored 

 friable limestone, the result of the breaking down or decompo- 

 sition of coral. It rarely makes bluffs on the coast of more 

 than 20 or 30 feet in height, but has been penetrated by wells 

 between 150 and 200 feet deep without passing through it 

 " -"■ ^ -ariable width of from a few hundred yards 



■ >City, 

 J wide^it illustrates beautifully the phe- 

 nomenon of change in lithological character of the same beds, 

 ioward Its margins in this vicinity near what was at that epoch 

 ttie mouth of the Jaina river, a few pebbles begin to appear, un- 

 naistakably attributable to the hills of the upper Jaina. Pro- 

 ceedmg northward, or toward the former coast, these pebbles 

 oecome more numerous and the lime less pure, until eventually 

 tne same stratum can be traced into a common shore gravel, 

 evidently the product of the river, and without a perceptible 

 ^^ceof lime. Further; in going east from the neighborhood 

 01 the Jaina, but along the ancient coast, the pebbles agam dis- 

 appear and the shore margin of the deposit becomes, as might 

 oe anticipated, sand ; while farther out the limestone belt con- 

 nues m the position of the former reef 

 iNo volcanic rocks have been encountered in the course of our 

 f felons except in the mountains north of Bani, where we 

 ^Is of fetd^^^ dike of black porphyiy with large white crys- 



