602 REVIEWS 
formation) in the Montana group, and that they are strictly equivalent to 
the Belly River beds of Canada. The authors believe that the Eagle 
formation marks the base of the Montana group, that the Bearpaw shales, 
Judith River beds, Claggett, and Eagle formations belong to the Montana 
group and are “equivalent to the Pierre as that term is generally under- 
stood,” and that ‘‘the use of the term Fox Hills as a formation or horizon 
name outside of the original area in South Dakota is of doubtful propriety.” 
C. W. W. 
The Limeless Ocean oj Pre-Cambrian Time. By REGINALD A. DALY. 
(Reprint from American Journal of Science, Vol. XXIII, Feb- 
ruary, 1907, pp. 93-115.) 
The concertion of limeless ocean is urged as an explanation of the 
absence of fossils in non-metamorphic pre-Cambrian rocks. In Eozoic 
time the lime-salts inherited form Azoic time were precipitated as carbon- 
‘ ate, because of the production of ammonium carbonate by decomposing 
organic matter. This and other conclusions are based on premises some 
of which are observational and sound, but others are postulates and deduc- 
tions of indeterminate value. Perhaps unintentionally the author (p. 113, 
premises 9, 10, 11, and p. 100) has left the impression that the CaCO, of | 
the sea has been always derived mainly from pre-existing limestone, instead 
of from decomposed silicates. From the hypothesis interesting deduc- 
tions are made as to the early development of the hard parts of organisms. 
C. W. W. 
Rate of Recession of Niagara Falls. By G. K. GILBert. Accom- 
panied by a Report on the Survey of the Crest. By. W. CARVEL 
HALL. _-(U.'S: ‘Geological: Survey, Bulletin No. 300)))(Pp.731, 
11 plates. Washington, 1907. 
‘““The rate of recession of the Horseshoe Fall, or the rate of lengthening 
of the Niagara gorge, during the sixty-three years from 1842 to Ig05 is 
found to be 5 feet per annum, with an uncertainty of 1 foot. For the 
thirty-three years from 1842 to 1875 the rate was apparently slower than 
for the thirty years from 1875 to 1905. ‘The rate of recession of the Ameri- 
can Fall during the seventy-eight years from 1827 to 1905 was less than 
3 inches per annum.” The latter figure is of interest to geologists because 
somewhat representative of the river’s activity in gorge-making when the 
volume of water was much less.” C. W. W. 
