-,2 ;.'•;'. • ::..:••••.•.• SEA AND LAXD 



studies endeavor to acquire certain general notions as to the 

 \va)' in which energy comes to, and acts upon, the surface of 

 the earth. He may well begin his steps towards this under- 

 standing by noting the fact that all the movements which 

 take place on the land and in the sea, from the storms to 

 the pulsations of his own heart, represent the action of forces 

 which oricrinate in the sun. From that orreat master of the 

 solar system there goes forth such a tide of energy in the 

 form of light and heat, that even the small share which falls 

 upon this little globe is in quantity vast almost beyond under- 

 standing. Some conception of it, however, may be obtained 

 in the following manner by a simple experiment. Let the 

 observer put in a vessel containing water at a temperature 

 of 32° Fahr., or just above the freezing point, a pound of ice. 

 Let the vessel be placed over a fire, so that the time required 

 to melt the lump of ice may be noted. It is well, indeed, to 

 have two vessels, each with the same amount of water and 

 of like temperature, the one wdth all the ice it wnll l^oat, and 

 the other without any frozen water. It will be easy to note 

 in this trial that a great amount of heat is taken up, or, as 

 the jjhrase is, rendered latent, in melting even a small cpiantity 

 of ice. But in a single day there comes from the sun to 

 the earth enough energy in the form of heat to melt about 

 8,000 cubic miles of ice, or enough to cover the area of the 

 State of Massachusetts to the depth of, say, 5,000 feet. It 

 is Avell to remember that the amount of heat which comes 

 forth from the interior of the earth in the same period prob- 

 ably does not exceed the (quantity required to melt somewhere 

 about 100 cubic miles of frozen water. 



When it comes to the surface of the earth, a considerable 

 amount of the solar heat goes quickly away again, by radia- 



