1905] TRANSEAUBOGS OF THE HURON RIVER VALLEY 421 



heat for a longer time. Consequently on cloudy days and following 

 a sudden 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 



FIG. 5. Diagram showing temperatures of the air and the substrata in the 

 several plant societies. 



is a 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 air 

 as in the case of a sphagnum- covered area the loss of heat by this 

 process is most effective in preventing the penetration of heat below 

 the surface. 



In the case of drained soils, the most effective agent in raising 



