1 88 1. 23 Trans. N. V. Ac. Set. 



apparently by a "continental " up-lift, whereby large areas of marine 

 deposit were raised without folding or disturbance. Professor Cleve 

 suggests that this movement may have been accompanied by a sinking 

 of part of the sea-bottom in the Caribbean region to the south-east, 

 and that, on the limit between the areas of rise and of depression, fis- 

 sures and faults may have occurred, through which these volcanic out- 

 breaks of the Leeward islands found exit, in the Post-pliocene time. 



DISCUSSION. 



Mr. A. A. JULIEN confirmed the accuracy of these petrographical 

 distinctions of the rocks of the Lesser Antilles, from the results of 

 observation during a residence of four years on Sombrero and vicinity. 

 The island of St. Eustatius consists mainly of volcanic ashes in a thick 

 tabular and horizontal stratum with vertical faces along its coast. 

 This is flanked on the south end by a volcanic cone with extinct crater, 

 of which the botto'm is occupied by a plantain plantation, but the sides 

 are bare, and consist of a dark basaltic rock ; and on the horth end by 

 two lower cones, not visited but probably volcanic. On the island of 

 Saba the rock is light colored, rich in crystals ot sanidine, and appar- 

 ently a trachyte, constituting a remarkably sharp volcanic cone, with its 

 sides deeply furrowed from top to bottom by eroded ravines ; certain 

 depressions upon the summit, resembling craters, present in some 

 localities sulphur deposits which have been found of commercial impor- 

 tance. 



However, the conclusion of Prof. Cleve, as to the recent age and 

 eruptive character of most of the crystalline rocks of this region, 

 appeared surprising in view of their metamorphic associates, and of 

 their similarity to those of the Archsan areas identified by Hartt in 

 Brazil. It was a question whether a nucleus of Archaean, or, at latest, 

 metamorphic pre-Silurian rocks, in general highly tilted, does not form 

 the axis of such islands as St. Martin, St. Barts, etc. 



Prof. D. S. Martin questioned whether a corresponding movement 

 of disturbance should not be also found in thie Cretaceous strata of a 

 region no farther removed than that of the vicinity of our own Gulf coast. 



Dr. J. S. Newberry remarked that the importance of the subject of 

 the age and origin of these crystalline rocks still demanded their re- 

 examination and a review of Prof. Cleve's conclusions by some worker 

 ot experience in this peculiar tield. One of the most interesting topo- 

 graphical features on this continent consisted in the line or axis of ele- 

 vation marked by the Windward Islands, separating the deep basin of 

 the Gulf of Mexico on the one side from the abyss of the Atlantic 

 Ocean on the other. It presents a prolongation and connection of the 

 mountain chains which run along the eastern border of the North and 



