178 



ANALYSIS OF THE ENVIRONMENT 



tity of water bound in chemical combination 

 vvithin the hthosphere or any knowledge 

 about its possible occurrence in molecular 

 or dissociated form in the interior of the 

 earth. 



In considering these estimates" and their 

 implications, one is struck by the impor- 

 tance of the role played by the relatively 



ICE 



Pure ice is somewhat hghter than pure 

 water. It has a density of 0.92 and floats 

 even without the presence of air bubbles 

 that are often enclosed. It forms a soHd 

 covering for the unfrozen Uquid below and 

 so preserves the liquid habitat of most 



ATMOSPHERIC VAPOR 



CLOUDS 



Fig. 39. The hydrological cycle. ( Modified from Meinzer. ) 



insignificant amount (in proportion to the 

 whole) of water carried by the atmosphere. 

 In one way the smallness of the amount of 

 atmospheric water enhances its importance, 

 since its distribution frequently acts as a 

 Limiting factor in the distribution of plants 

 and animals. 



aquatic animals, even in cold climates. Ice 

 provides an extension of the solid sub- 



* The estimates given are based on data 

 given by Bernard, 1942; Mathes, 1942; 

 Sverdrup, Johnson, and Fleming, 1942: 

 Meinzer and Wenzel, 1942; Fuller, 1906; and 

 Wildt, 1942. 



