4 FIRESIDE SCIENCE. 



of the strata but upon the character of the rock 

 which prevails. The arrangement of percolating 

 streams below the earth's surface is of course en- 

 tirely unseen, but it must be, nevertheless, very 

 wonderful and interesting. The water which flows 

 out of an orifice in a rock or in the soil at a given 

 point, may have fallen as rain upon a surface ten, 

 twenty, or five hundred miles distant, and the sub- 

 terranean river may have wandered in darkness down 

 the sides of distant mountains through sand, marl, 

 and rock fissures, into the valleys below. From 

 thence, it may have been forced up the sides and 

 over other mountains of less altitude, by the well 

 known law which governs fluid equilibrium, until 

 it reached the surface at a favorable opening, and 

 escaped as an ever gushing spring. The geological 

 formations which prevail in any section govern the 

 conditions under which water flows from the earth, 

 whether it be with eruptive force, or feebly, as do 

 most springs that come under our observation. 

 We must remember that the great bulk of the sed- 

 imentary rocks, and all of the unstratified, are 

 wholly impervious to water, and in their upheaved 

 condition, it is only through the breaks and seams 

 which prevail that it can find its way into the great 

 subterraneous sand deposits and cavities which ex- 

 ist in many localities. If the geological conditions 

 are such as to afford insufficient surface drainage, 



