Bibliographical Notices. 135 
George Darwin’s papers on “ Tidal Evolution,” and by calculations 
by himself, Prof. Robert Ball, and Mr. A, R. Wallace, on the pro- 
bable time taken in the deposition of the stratified rocks. Taking 
these at a thickness of 177,200 feet, 3,000,000 square miles as the 
area of deposition (on coast-lines for about 30 miles to sea), the 
land-surface exposed to denudation as 57,000,000 square miles 
(nineteen times the area of deposition), and the present rate of denu- 
dation as 1 foot in 3000 years, the duration of Geological Time 
equals about 28,000,000 years. Itis to be remembered that it is 
highly probable, Dr. Haughton thinks, that during all geclogical 
time down to the close of the Tertiary period, the temperature of 
the Earth’s atmosphere was higher than at present, and the more 
so the further back we go—the necessary consequences being greater 
evaporation, greater rainfall, greater denudation, greater trade- 
and antitrade-winds, greater ocean-currents, and greater facilities 
for spreading and depositing submarine strata. 
It is now thought by Prof. Robert Ball that the great tides 
caused by the lesser distance of the Moon from the Earth (within 
some 50,000,000 years) were pregeological. Mr. J. 8. Newberry 
thinks that the Eozoic rocks in North America do not show evidence 
of tides much greater than those now in action on the Atlantic 
shores of that region (including, however, the 70-ft. tide of the Bay 
of Fundy). 
Dr. Haughton then took up the “ Supposed Causes of Changes in 
Geological Climates.” 
I. The Supposed former effects of Star-heat, or warm portions of 
space, suggested by Poisson. 
Il. The Obliquity of Heliptic. “As this speculation postulates 
the change of position of the Earth’s axis in space, it must be set 
aside as irrelevant.” 
III. Changes in Position of Pole, that is of the Earth’s axis 
within the Karth itself, causing the poles and equator to shift their 
positions. Such a change of position of the axis of rotation inside 
the Earth could be produced by changes of land and water, but not 
to nearly so great an amount as required to account for the former 
existence of tropical and subtropical animals and plants at places 
now in frigid climates, but yielding fossils representing such faunas 
and floras. Mr. G. Darwin, basing his calculations on the area of 
the ‘‘ Pacific depression,” finds the maximum change of latitude 
would be 3°, or 210 miles; and Dr. Haughton, taking Europasia 
(as elevated since the commencement of Tertiary times) for his hasis, 
finds the change of latitude caused by that elevation to be only 1°, 
or 70 miles, 
On the contrary, there is evidence of change of latitude to 
the extent of 50°, or 3640 miles, with Silurian corals; 43°, or 3010 
miles, with Liassic fossils ; 36°, or 2520 miles, with the fossil plants 
of Grinnel Land ; 30°, or 2100 miles, with the fossil plants of Disco. 
IV. Eccentricity and Perihelion-Longitude of the Earth’s Orbit, 
producing a secular variation in climate. This was proposed by 
Adhemar, and worked out more fully by J. Croll, J. J. Murphy, and 
