1890.] Geology and Palæontology. 67 
GEOLOGY AND PALÆONTOLOGY. 
Archean Characters of the Rocks of the Nucleal Ranges 
of the Antilles.!—During a visit this year to the southeastern 
part of the island of Cuba, the speaker had made some exam- 
inations 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 examination of the specimens under 
the microscope, it seems highly probable that these rocks, instead of 
being igneous extrusions 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 argument 
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. 
5. 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 phosphorous and in 
the pyrite and (more sparingly) chalco-pyrite 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. 
1 Read by Dr. Persifor Frazer at the Bath Meeting of the British Association, 1888. 

