518 Notices of Memoirs—Dr. P. Fraser—Rocks of the Antilles. 
III.—Arcuran CHARACTERS OF THE Rooks oF THE NUCLEAL RANGES 
or THE ANTILLES. By Dr. PErstror FRazer.' 
De a visit this year to the south-eastern part of the island of 
Cuba, the speaker had made some examinations of the rocks 
which form the nucleus of the spurs of the Sierra Maestra, and there 
is strong reason to believe of the axial range of the entire island and 
of Jamaica, Santo Domingo, Puerto Rico, and the Windward Islands 
as well. From the field observations there made, and an examina- 
tion of the specimens under the microscope, it seems highly probable 
that these rocks, instead of being igneous extensions of the Tertiary 
period and later, are in reality of much earlier date, and may not be 
entirely volcanic. 
The considerations which support this view are— 
1. Microscopic analysis shows immense alteration to have taken 
place, and consequently a very long period to have elapsed. 
2. The complexity of the congeries of rocks forbids the hypothesis 
of their having been derived from one mass. Where this congeries, 
therefore, is unconformably adjacent to the Tertiary, there can be no 
reasonable doubt that the crystalline rocks are the elder. This point 
of view was suggested by Mr. Teall, who would consider the argu- 
ment valid also for the contact with the Cretaceous, and perhaps 
older series. It is difficult to see why it should not hold equally 
good for the contact between these crystalline and the Paleozoic 
rocks as made out by De Castro near Cienfuegos, etc. 
3. The characters of the several associated rocks are those which 
one finds united in very many Archean regions throughout the world. 
4, The products of alteration of these rocks are similar to those 
which one finds in the districts just alluded to. 
d. The chemical peculiarities of the iron ores found in contact 
with these rocks are similar to those which one finds in the ores of 
the Archean regions, both in the low percentage of phosphorus and 
in the pyrite and (more sparingly) chalcopyrite disseminated through 
the ore, and in other respects. 
6. If this nucleal mass had been forced up from the earth’s interior 
in a state of igneous fusion, there would not be now (as there are) 
abundant traces of stratification and structure, implying an original 
sedimentation. 
7. If-this mass had resulted from volcanic outflow, there must 
have been contact-phenomena, and changes induced on the surfaces 
of the rocks with which it was brought in contact. No such contact- 
alteration has been observed between these rocks and either of the 
three groups which meet them. 
8. The direction of the range, considered as a whole, lends support 
to the hypothesis that it is a fork of the Andes which, diverging 
from the main axis in Guatemala, traverses the peninsula of Yucatan, 
and in a symmetrical curve sweeps through the highlands of Cuba 
and Jamaica, Hayti, Puerto Rico, the Windward Islands, and the 
N.E. coast of Venezuela. This run of high land once inclosed the 
Caribbean as another Mediterranean Sea. 
’ Read before Section C, British Association, Bath, September, 1888. 
