TABLE OF CONTENTS. xxi 
Page. 
Theories of erratic blocks. 214 
Necessity of seeking a cause affecting the earth. 216 
Propositions necessary to the consideration of the subject. 216 
Evidences—(A) Refrigeration and contraction of earth. 217 
(B) Currents from polar regions.... 217 
Evident change of relative levels of land and sea. 218 
In discussing the causes, exclude all causes exterior to the earth. 218 
Desiccation of land not due to general cooling without change of form . 218 
Nor to unequal contraction of land and water. 218 
Nor to a change in the axis of rotation. 218 
Reason why it is evident that there has been a relative change of level. 219 
Causes to which such change of level may be ascribed, that have not been considered: 
1. An internal expansive force. 219 
2. Collapse by refrigeration by means of gravity. 219 
Mr. Hopkins’s researches on elevatory movements . 219 
Prof. Phillips’s reasoning on elevation and depression. 220 
Disturbance of strata due to a contraction of the earth. 220 
Diminishing heat of the globe...220 
Temperature of space. 221 
Change in length of the day consequent on refrigeration of the globe. 221 
Periods of time to render such change sensible. 221 
Length of day not varied sensibly for 2,000 years . 221 
Causes of polar currents: 
1. Refrigeration of the globe... 221 
2. Upheaving of land or bed of the northern ocean. 221 
3. To compensate disturbed equilibrium of the eartli; disturbed spheroidal form due 
to its rotation, in consequence of the gulf stream and varied mean temperature 
of the polar and equatorial regions. 221 
1st cause already discussed and found sufficient. 221 
2d cause, no evidence... 221 
3d cause, permanent as the ocean and rotation of the earth. 222 
Discussion of 3d cause; dynamical laws regulating these currents. 222 
Influence of mean temperature of polar and equatorial regions on the ocean currents, 222 
Mr. Redfield’s observations on Labrador current.. 222 
Drift ice of northern Atlantic presses westward toward American coast. 222 
Dynamical law causing this effect. 222 
Flow of Labrador current and gulf stream. 222 
Action of these on icebergs... 222 
One superposed on and flowing in the other. 222 
These currents local examples of the compensating equatorial and polar cur¬ 
rents of the earth. 222 
Have acted in all time past, and will all time to come. 222 
