REVIEWS 623 
A corollary of some interest, not mentioned by the author, relates 
the history recorded by recessional moraines to that associated with 
Niagara gorge. From the beginning of the last ice retreat at Cincin- 
nati Taylor counts seventeen moraines to Rochester, beyond which 
point new conditions enter, making the continuance of the analysis a 
matter of great difficulty. But just at the close of the term represented 
by these moraines the Niagara began its work, so that the moraine 
history is complemented by the river history. ‘Together they represent 
all the time since the latest ice maximum, a period whose measure- 
ment in years is far more valuable to science than the determination 
of the age of the great cataract. Postulating the astronomic cycle of 
the precession of the equinoxes as the cause of the morainic cycle, tine 
approximate time covered by the morainic history is computed (by the 
reviewer) at 315,000 years. This is so long a period in comparison 
with the most ample of modern estimates for the age of the Niagara 
that the uncertainty as to Niagara’s age is of little moment in consider- 
ing the sum of the two periods. Broadly stated, the hypothesis that 
the recessional moraines are functions of the precessional cycle esti- 
mates the time since the last maximum of glaciation at 300,000 to 
400,000 years. 
GLK G. 
The Influence of the Carbonic Acid in the Air upon the Temperature 
of the Ground. By PROFESSOR SVANTE ARRHENIUS. Philo- 
sophical Magazine and Journal of Science, Vol. XLI (Fifth 
Series) 1896, pp. 237-276. La Revue Générale des Sciences, 
Mai, 1899, pp. I-22. 
Professor Arrhenius was led to investigate this subject by the debates 
among the Swedish geologists upon the cause of the glacial and inter- 
glacial climates of the Pleistocene. The conclusion that none of the 
current hypotheses are satisfactory or at all competent to explain the 
observed phenomena led him to calculate the quantitative effect of any 
given variation in the amount of atmospheric carbon dioxide upon the 
temperature of the earth’s surface. The fact that the carbon dioxide 
and water vapor are the chief agents in retaining the heat radiated from 
the earth’s surface had long been known qualitatively and even the 
relative values of the selective absorption of radiant energy for the 
various atmospheric gases had been determined, but it remained for 
