1905] TRANSEAU—BOGS OF THE HURON RIVER VALLEY 421 
heat for a longer time.’ Consequently on cloudy days and following 
asudden lowering of the air temperature, the surface bog-water 
temperature stands above that of the drained and undrained soil. 
When we compare the effects of loss of heat from a free water 
surface and a saturated humus soil surface due to evaporation, there 
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Fic. 5.—Diagram showing temperatures of the air and the substrata in the 
several plant societies. 
ia marked difference due to their specific heat. The humus will 
be cooled more rapidly by the evaporation of a given amount of 
Water. Where so large an evaporating surface is exposed to the on 
aS in the case of a sphagnum-covered area the loss of heat by ; 
Process is most effective in preventing pet mouse? a 
the surface. i 
In the case of drained soils, the most effective agent ™ 
raising 
