154 SNAKE RIVEE PLAINS OF IDAHO. [bull. 199. 
for each 45 feet below the stratum of no seasonal variation. The can- 
yon springs also, on the supposition that the rate of increase of heat 
with depth is normal, indicate a higher temperature than would be 
expected from the depth of the localities where the}^ emerge below 
the level of the adjacent plains. 
Chemical changes, as well as movements in rocks, may also produce 
abnormally high temperatures, which might be imparted to the waters 
of any of the types of springs enumerated above, but which are most 
apt to be felt by fissure springs. 
The phenomenon of a hot and a cold spring near each other, which 
sometimes occurs, can be easily explained by reference to the dia- 
grams given above. A hot fissure spring supplied from a deep source 
may evidently occur near a cold hillside spring, the association .of the 
two being simply accidental. 
There is much that is interesting in the chemistry of spring water, 
and in the way in which hot springs especially deposit material — most 
commonly calcium carbonate and silica — on reaching the surface, but 
this phase of the study can not be considered at present. 
SIMILARITY BETWEEN SPRINGS AND WELLS. 
Each of the varieties of springs enumerated above is represented by 
wells. 
The ordinary wells, especially in humid regions, are supplied by 
percolation from the adjacent portions of the porous beds they pene- 
trate, and are similar to hillside springs. When they are supplied at 
a depth of about 50 feet below the surface their temperature, when 
inclosed, is approximately that of the mean annual temperature of the 
locality where they occur. The water in them rises and falls with 
variations in the position of the water table, and if the surface of sat- 
uration sinks below their bottoms they become dry. Deep wells, 
usually obtained by drilling, which penetrate pervious strata in which 
the water stands at a definite horizon and which in many instances, as 
is frequently stated, can not be lowered by pumping, are homologous 
to canyon and cave springs. The water is either not under pressure or 
not under sufficient pressure to cause it to rise to the surface, and has 
a constant temperature which is somewhat higher than the mean 
annual temperature of the locality. Artesian wells are essentially 
artificial fissure springs, and have a constant and frequently a high 
temperature. 
RELATION OF SPRINGS TO CLIMATE, TOPOGRAPHY, AND GEOLOCY. 
In addition to the fact that all springs are dependent on precipita- 
tion for their water supply, there is a relation between the amount of 
water supplied and the topographic and geological conditions which 
determines what variety of spring will result. 
