Position of the Axis of the Earth’s Crust. 231 
having occurred. 
The evidence of the extreme refrigeration of this portion of 
the earth at the Glacial Period is constantly receiving fresh cor- 
roboration, and various theories have been proposed which ac- 
count for this accession of cold in a more or less satisfactory 
manner 
Variations in the distribution of land and water, changes in 
the direction of the Gulf Stream, the greater or less eccentricity 
of the earth’s orbit, the passage of the solar system through a 
cold region in space, fluctuations in the amount of heat radiated 
by the sun, alternations of heat and cold in the northern an 
southern hemispheres, as consequent upon the precession of the 
equinoxes, and even changes in the position of the center of 
ar axis, have all been adduced as causes calculated to produce 
the effects observed ;.and the reasoning founded on each of these 
ta is no doubt familiar to all. 
James, the Astronomer Royal, Professors Beete Jukes and Hen- 
hessy, and others, but throughout the discussion the principa: 
question at issue seems to have been whether any elevation 
* Méc, Cél, vol. v, p. 14. + Atheneum, Aug. 25, 1860, dc. 
