1891.] Geology and Pateontology. 363 
hronika, Chadophlebis augustifolia, Sequoia acutifolia, Podzamites 
nervosa, and Oleandra artica 
Secular Disintegration of Rocks.—In a recent paper Mr. 
Raphael Pumpelly insists that the recognition of the importance of 
secular disintegration is essential to the proper interpretation of some 
of the most difficult points in the study of the crystalline schists. It 
gives a key to the problem in the Green Mountains, N. H. He 
instances Iron Mountain, Mo., as a convincing illustration of a deep- 
reaching disintegration in pre-Silurian time, in a region which has not 
been folded. A mantle of disintegrated rock would be easily and 
quickly removed by the breaching action of the advancing sea line. 
“ If we substitute this process.in each period for the accepted one of 
slow erosion and breaching of hard rock, we shall,” says the writer, 
“have to materially reconsider our time scales, in so far as they depend 
upon the rate of accumulation of, detrital materials.” (Bull. Am. 
Geol. Soc., Vol. II.) 
The Origin of the Bahama Islands.—A careful study of the 
geography and geology of the Bahamas leads Dr. Northrop to declare 
himself in favor of a theory of elevation of these islands, instead of 
subsidence. The main facts that bear on the question of the most 
recent movement are as follows: 
1. The soft calcareous mud on the west coast of Andros grows 
gradually harder and harder toward inland. 
2. The depth of the fine calcareous deposit close to shore, 
3-. The extension of the pine forest. 
4. Mangroves were found high above water-mark apparently dying, 
_ but none were seen in situations that indicated that the water was 
becoming too deep for them. 
Note was taken of the extensive erosion of both the surface and the 
shore line of the islands. (Trans. N. Y. Acad. Sciences, Oct. 13, 1890.) 
> 
Geological News. — General.—In a recent paper on the 
“Resources of the Black Hills,” Mr. Robert T. Hill says that this 
region is certainly capable of supporting a large and prosperous popu- 
lation. Aside from its agricultural resources and scenic beauty, it 
possesses bituminous coal and coke of good quality, lubricating and 
illuminating oil, with a possibility of natural gas, ores of precious 
metals, and of iron, copper, and tin. (Am. Inst. Mining Engineers, 
Sept., 1890) 
Paleozoic.—Prof. Alexander Winchell calls attention to some 
idin rocks in the vicinity of Echb Lake. They consist of rugged 
