1891.] Geology and Paleontology. 277 
Age of the Glacial Period.—In discussing the cause of the 
Glacial period, Mr, Warren Upham discards the astronomic theory, 
since it seems wholly untenable in view of the geologic evidences that 
not many thousand of years have passed since the departure of the 
_ ice-sheets. The measurements of the gorge and Falls of St. Anthony, 
the surveys of Niagara Falls, the rates of wave-cutting along the sides 
of Lake Michigan, the rates of filling of kettle-holes, and the rate of 
deposition in the Connecticut valley at Northampton, Mass., all indicate 
that the time since the Glacial period cannot exceed 10,000 years. 
Mr, Upham cites evidence in proof of the theory that the cause of 
the Glacial period was great’ uplifts of the glaciated areas, probably 
in conjunction with important changes in the course and volume of 
the warm ocean currents. (Am. Geol., December, 1890. ) 
Geological News.—General.—In a recent paper Mr. E. W. 
Claypole replies to the four leading arguments for the permanence of 
the ocean abysses and the continental masses. While he does not advo- 
cate the extreme views of Forbes, he gives many good reasons for not 
adopting the permanerce theory in its entirety (Bull. Geol. Soc. Am., 
: Vol. II., p. 10). Contrary to the general belief that coral reefs are 
not formed in the western waters of the Gulf of Mexico, Prof. Heilprin 
and Frank C. Bahn found thirteen species of corals in the neighborhood 
of Vera Cruz. There are a number of reefs consisting of detached 
islands extending eastward from the coast rearly six miles. In some 
cases the greatest development of coral growth is on the lee or shore 
side. They belong to the same category as the Florida reefs and banks 
(Proc. Acad. Nat. Sciences, Phila., 1890, p. 303). In discussing the 
phosphates of Redonda, a volcanic island in the Caribbean sea, Prof. 
- H. Hitchcock maintains that the enormous quantity of mineral 
ftdudes the possibility of its having been derived from the droppings 
of birds, and suggests that it may have come up from below as a phos- 
phuret, which has since changed its character through oxidation and 
hydration (Bull. Geol. Soc. Am., Vol. II., p. 6). According to 
D’Invilliers, the output of guano from the Island of Nevassa is between 
sixty and seventy-five tons per day. There are two varieties, the gray 
and the red ; the former is the more valuable, since it contains a less 
percentage of sesquioxide of iron and alumina (Bull. Geol. Soc. Am., 
Vol. IL, pp. 75-84). , 
Paleozoic.—Mr. A. Smith Woodward considers Ctenodus inter- 
7uptus the Lower Carboniferous representative of the well-known 
C. cristatus (Rept. Yorkshire Philos, Soc., 1889). = According to 
