THE GEOLOGY OF MINEEAL SPRINGS. 
205 
solubility* of strata uponwbicb tbe formation of rivers depends. 
Every stratum beneath the first impermeable one would have 
remained intact and the great law of the equality of w^aste^ in 
virtue of which every formation contributes its share to the 
re-arrangement of land and water_, w'hich is perpetually going 
on would have had no existence. Of course there would have 
been no springs, for as there would have been no mountains or 
hills through which the water could percolate to lower levels 
and rise up again through the first fissure which it meets, as 
it does now, it would have stood at a dead level everywhere. 
In fact, the earth would have been one vast swamp, covered, 
possibly, by a luxuriant vegetation, but totally unfitted for the 
habitation of man. Such was, in all probability, its state in 
those long-passed epochs, whose relics have come down to us 
in the carboniferous, oolitic, and other early formations. 
From these considerations it will be evident that both the 
abundance and the peculiar character of the springs in any 
given locality, will be entirely dependent on the geological 
conditions which prevail there. For instance, their eruptive 
energy, that is, the force with which they rise, or the height 
above the surface of the ground to which they are projected, 
will be determined by the existence in the neighbourhood of 
elevations which, by the fall that the water percolating through 
them acquires, will enable it, by the well-known law which 
governs fluid equilibrium, to rise to a level corresponding to 
that from which it has descended. This is well shown in the 
fourth of our illustrations, where c represents an elevated 
tract of country, immediately beneath which the porous stratum 
h crops up on the surface. The rain-fall of the land above c 
will gradually percolate through this stratum until it either 
makes its way up a natural fissure, or an artificial boring at e, 
where it will form a vigorous spring, or spontaneously exudes 
as a weak one at the other outcrop of the stratum at d. 
But it is as much to the character as to the inclination of 
the strata of a district that the distribution of its springs is 
due, and more particularly to the mutual relations of the 
porous and impermeable formations which it contains. The 
proportion which the former of these bear to the latter is, in 
the majority of cases, very small. When we remember that it 
is only sand, marl, gravel, and other similar loose materials 
which allow of the percolation of water, and that the great 
bulk of the sedimentary formations, and all the unstratified 
ones, are nearly, if not quite, impervious to it, we shall have no 
difficulty in understanding the obstacles which they present to 
* By the term solvMliUj here is meant not so much diemical solution as 
mechanical clisintesfration. 
o 
