IMPORTANT ELEMENTS AND MINERALS 51 
is the solid form of water. The liquid form, or water, 
is present in all rocks, both chemically combined, 
and passing freely through them. While quarries and 
mines show that water is constantly present among 
the crevices, a careful study reveals the fact that it 
also exists between the pores of even the densest rocks. 
It is found in the air as a vapor, from which it 
descends to the earth as rain or snow, either remaining, 
flowing away, entering the earth, or passing back to 
vapor. In the ocean there are about 300,000,000 cubic 
miles of water. 
This substance is commonly either a vapor or a 
liquid; but in the winter it may become a solid with 
crystalline habit, and in some of the arctic lands, and 
on high mountain tops, the solid form is always present. 
Not only does it exist in great masses in the form of 
glaciers, but, in some of the colder regions, the soils are 
permanently frozen to a depth of several hundred feet. 
While water is very important in these conditions, 
it also plays a notable part in the changes within the 
crust, through which it is always moving, dissolving 
here and depositing there. It is the chief agent by 
means of which the operations within nature’s grand 
chemical laboratory, the earth’s crust, are carried on; 
and we shall have frequent occasion to note its impor- 
tance in geological action. 
