UNDERGROUND WATER 145 
(Fig. 76). These are really minute landslips of infini- 
tesimal degree. A single one is minute and unim- 
portant, but the countless millions caused by every 
rain, represent a great sum total in the course of time. 
Springs. — A part of the underground water, after a 
short passage, returns to the | 
air along some channel. Often 
this flow is sufficiently perma- 
nent to form a spring, either 
one always welling, or one that 
has water only in moist seasons. 
Every one is familiar with these, 
and there are far more than we 
commonly see; for upon many 
hillsides are damp, bogey places, 
which, if the vegetation were 
removed, would become perma- 
ei oS 
nent springs. a ae 
Fie. TE; 
under which springs may be Fresh sear on a cliff in a stream 
valley, where the creek has 
formed. Where the under- caused a slip by undermining. 
There are several conditions 
ground rivers that are shaping 
caverns appear at the surface, there are true springs, 
often large and permanent (Figs. 67 and 69). Again, 
a break or fissure in the rocks, may reach down 
to a layer containing water whose temperature is 
high; and where this reaches the surface (Fig. 72), 
L 
