1881. 23 ET ANS INE VS AG C2. 
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 bottom is occupied by a plantain plantation, but the sides 
are bare, and consist of a dark basaltic rock; and on the north end by 
two lower cones, not visited but probably volcanic. On the island of 
Saba the rock is light colored, rich in crystals of 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 Archaan areas identified by Hartt in 
Brazil. It was a question whether a nucleus of Archzan, 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 the 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 field. 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 
