TJie Evolution of Climates. — Man son. 113 
When solar energy was arrested so as to permit the areas now- 
covered by the meadows of England, by the olives of France 
and Italy, by the cedars of Lebanon, by the palms and bananas 
of Nicaragua to be glaciated, no suspension of these conditions 
must be looked for in the tropical plains of Brazil. 
Review. 
The varying degrees of distinctness of glacial evidences are 
so important in their bearing upon the climatic evolution now 
in progress upon our plartet, that at the risk of repetition thev 
will be reviewed. Cold temperate areas show unmistakable ev- 
idence of having but receiitly lost their covering of glacier ice.* 
Near the base of glaciers within the torrid zone and upon 
less elevated lands in warm temperate latitudes, the same dis- 
tinctness of recent retreat can be observed. 
At or near sea level in regions near the polar circles, as in 
Alaska, Greenland, northern Europe and Asia, Patagonia, 
south Georgia, etc., this retreat has been so recent that it is 
within the range of history, and in very elevated tropical lands, 
in less elevated temperate lands and in polar regions glacier ice 
yet rests, and is yet retreating.t 
Whilst there are fluctuations in the advance and retreat of 
glaciers, the general result is that the integral of successive re- 
treats is greater than the integral of successive advances. This 
is a very marked characteristic over areas where the changes 
have been noted with great accuracy. 
The Temperate Age. 
At a period just antedating the Ice age fossil life has every- 
where recorded the existence of a warm temperate age. The 
life systems everywhere attest that a temperature correspond- 
ing to the warm temperate zones of to-day existed throughout 
l)oth hemispheres. Even in Brazil the remains of extinct gi- 
gantic mammals, corresponding to the fauna found in North 
*So recent has been this retreat that some geologists have been 
tempted to make mathematical calculations of the date based on the 
recession of modern waterfalls. 
tProf. Tarr noted the recent retreat of Greenland glaciers, Am. 
Geologist. Vol. XIX, No. 4, p. 263; instances of recent glacial retreat 
in tropical and temperate latitudes are elsewhere given. 
