OF SAISTTO DOMINGO. 



105 



I am not willino; to go to so great a length as that author in believmg that the 

 decay of the animal tissues whether of corals or shells, is the principal means of their 

 destruction and the consequent formation of the semi-pulverulent rock derived from 

 them. His Bermuda "chalk" is a small local deposit compared with the greater mass 

 of "Bermuda Stone," which from his description corresponds in character with the 

 rock making up the Bahama group and the Dominican coast limestone. Later the 

 same author, then Captain, now Major-General ISTelson, R, E., in his memoir on the 

 Bahamas* suggested additional sources for the material, but he does not in my 

 oj)inion lay enough stress on what must have been the main cause, the triturating 

 effects of wave-action aided doubtless, but not replaced by the various means that he 

 suggests. 



It is a misnomer to call this material "chalk." True chalk whether derived from 

 the English cliffs or elsewhere, is microscopically considered composed of hollow 

 grains. "It is made by accumulations of Rhizopod shells, and not of coral or shell 

 sand."t The West Indian rock is coral and shell sand, and is composed wholly, or 

 nearly so of amorphous solid grains. In external characters to the naked eye it 

 certainly resembles some varieties of chalk. Its nearly white color, softness, absence 

 of " grit," and its chemical constitution ally it closely to that mineral while its origin 

 and microscopic structure separate it. In view therefore of this difference and since 

 no name has ever been suggested to distinguish it, I suggest that of Antillite. 



As intimated above the " coast limestone " (our new Antillite) was formed as a 

 fringing reef at a considerable distance from the then coast line. This is beautifully 

 illustrated on the south side of the island, Imt more particularly in the region lying 

 north and northwest of Santo Domingo City. The mouth of the Jaina Kiver was 

 then at what is now the base of the higher hills at the back margin of the low-rolling 

 savanas. This stream as well as its neighbor the Isabella now a branch of the Ozama, 

 brought down great quantities of gravel and even large boulders, which were of 

 course deposited immediately along the coast and formed a gravelly beach. The 

 gravel was carried out to a distance of several miles from the mouths of the rivers 

 and made a sea-bottom of sand with pebl)les, constantly diminishing in size as th^ 

 distance from their source increased. The current evidently came from the west and 

 carried this debris eastward along the ancient coast, so that the deposit extends from 

 each old river mouth in a marked manner in that direction. The then insignificant 



* Quart. .Jour. Geo!. Soc, Vol. IX., pp. 308, 212. "This calcareous mud is derived not merely from the commi- 

 nution and decompdsition of corallines and corals, and from the exuvite of Foraminifera, Mollusca, Echinoderms, 

 Crustaceans, &c., but also from the ftecal cjcctamenta of Echinoderms, Conchs and Coral-eating Fish {Scuri, §'c)." 



•f Dana, Manual of Geol., p. 753. 



A. P. S. VOL. XV. 2a. 



