404 KANSAS ACADEMY OF SCIENCE. 



it is condensed into rain or snow and its surplus heat liberated in the 

 air. Thus is the climate ameliorated at both ends of its journey. 



After all, we discover, on reflection, that water, after carrying its 

 load of earth from the mountains to the sea, does not return empty 

 handed, On the contrary, it serves a useful purpose wherever it goes ; 

 for, after carrying its load of earth from the mountains to the sea, it 

 carries back with it a load of heat from the sea to the mountains. 



Snow and ice, too, may be evaporated and all dried up without 

 liquefaction. This is in case dry winds from the interior blow over 

 them. Evaporation of snow, of course, abstracts heat from the sur- 

 roundings ; but dry cold air is less keenly felt than damp cold air. 

 Besides, the heat taken up is sooner or later returned to the air. 



OTHER PROPERTIES OF WATER. 



Water has its greatest density at 3.9° C, equivalent to 39.2^ F. 

 Above that it expands slightly for every increase of heat up to 212°. 

 It then suddenly absorbs a very large quantity of heat ; increases 

 vastly in size ; and is converted into steam. So far as water is con- 

 cerned, 39. 2^^ F., might be called its zero of temperature, where it is 

 neither hot nor cold. Below 39° water increases in size for every in- 

 crement of cold until 32° is reached in fresh water. At 32° it absorbs 

 enough cold to reduce the same quantity of water from 176° down to 

 the freezing point, increases one-eleventh in size, and takes the solid 

 form. 



Pure water holds to salt, as in sea-water, with a tenacity equal to 

 four degrees of temperature ; that is, sea- water does not freeze at 32° 

 but continues liquid and to increase in size till 28° is reached ; then 

 the water freezes, squeezing out the salt. As the amount of salt in- 

 creases, the degree of cold required to freeze the water necessarily in- 

 creases. Ice, being only eleven-twelfths the weight of water, floats on 

 the surface of the water. 



Then, while ice may and does transmit radiant heat from the sun, 

 as glass does, permitting objects under the ice to become slightly 

 warmed by solar heat, it is a very effective barrier against the admis- 

 sion from the air of cold that comes through convection. It thus acts 

 as a protecting blanket, permitting passage of heat from the sun, yet 

 effectually preventing the escape of heat from the water and prevent- 

 ing the cold above from passing into the water, thus conserving the 

 life below. 



The change of form from water to ice is progressive, not sudden 

 like the solidifying of melted lead, iron, or mercury. This is on ac- 

 count of the very large amount of cold which the water must absorb 

 from the air in order to be converted into ice. These are all very im- 

 portant features, upon which the well-being and happiness of all 

 forms of life depend. 



