1903.] NATURAL SCIENCES OF PHILADELPHIA. 397 



Iron Co., near Firmeza. (1) Diorites, some of which contained much 

 altered hornblende and viridite (chlorite), the thin shdes filled with 

 microlites and the rocks traversed by epidote veins. (2) Dolerites, 

 diabase (gabbros), with chloritic ground mass, magnetite, rods of feld- 

 spar and some olivine. 



B. From the hills southeast of that in which the "East mine" was 

 located and about fifteen miles northeast of Santiago de Cuba. (1) 

 Garnet rocks with iron ore (sp. gravity 3.962). (2) Fibrous actino- 

 lite, and brown iron oxides partially altered to an epidotic mass. (3) 

 Iron ores (some showing cross lines like the Widmanstatten figures in 

 meteoric iron). 



C. From the Sietes Altares, about thirty-five miles east of Santiago 

 de Cuba. Orthofelsite porphyry (rhyolites), like those erroneously 

 referred to by the late Prof. H. D. Rogers as ''jasper," and later 

 recognized by the late Dr. T. Sterry Hunt as a mixture to which he 

 gave the general name " orthophyre " ; also like the Arvonian tuffs of 

 Hicks, near St. David's Head, Pembrokeshire, Wales. 



D. The specimens from the region of the La Plata mines were quartz- 

 ites containing hornblende, iron ores and, among the incidental min- 

 erals, a claret-red garnet. 



In the area described were found upon or associated with the erup- 

 tives sandstones, conglomerates and crystaUine limestones, laminated 

 iron ores with masses of pyrites not yet converted into the latter. 

 The alteration of the areas of contact in these rocks by the more recent 

 diorite dykes which cut them was evident. 



From the character and relations of these rocks I deduced a physical 

 continuity between the Archean of the mainland of the North American 

 continent and the skeleton of the Cuban orographic system. 



From the zoological and geological researches of Alexander Agassiz 

 in Caribbean and Mexican waters, and the careful studies by Gabb, 

 Crosby, Spencer and Hill, the probability of very great changes of 

 level in the Antilles since the close of the Cretacic period was estab- 

 lished, and this probability is fortified by several different fines of 

 proof, i.e., the ledges and shelves of the island borders, the wide distri- 

 bution of the white radiolarian limestones, etc., and finally petro- 

 graphic examinations of material from the several islands. 



Prof. Crosby pointed out orographic reasons for assuming a former 

 " bridge " {i.e., causeway) between the Greater and Lesser Antilles. As 

 he says, the mountains of "the northern arm of the island of San Do- 

 mingo point toward Cape Maysi on Cuba," and the northern range in 

 Cuba "regains the western trend and points directly toward Yucatan." 



