148 J. Croll—Cause of Mild Polar Climates. 
bringing the glacial state to a close. n this case there 
ought to be a succession of beds indicating the long continu- 
ance of cold conditions. Instead of this, however, we have a 
glacial bed immediately preceded and succeeded by beds 
indicating an almost tropical condition of climate. When 
we take this circumstance into consideration, along with the 
evidence adduced by Mr. J. S. Gardner as to the alternations 
of warmer and colder conditions in the South* of England and 
other parts of Europe during the Eocene period, the convic- 
ome geologists have maintained that the climatic condi- 
tions of the Tertiary period are utterly hostile to the Physical : 
Theory of Secular changes of Climate. The very reverse — 
however, is the case; for, as we have seen, several of the fact® — 
of Tertiary climate can be explained on no other principle tha? — 
that of the theory. ee 
I shall next consider the facts bearing on Arctic Intergla a 
cial periods, 
* Phil. Mag., November, 1868; ‘ Climate and Time,’ chap. xxi. 
