ORIGIN OF ROCK-SALY. 19 
must of necessity have been the drainage off saliferous and clay 
lands, This brings in river action There is evidence that a 
river or current from the north brought down, from a con- 
glomerate of the Old red-sandstone, the pebbles which we now 
find scattered in the Bunter sandstone. This river could furnish 
our lake with waters more or less saline, and while so doing 
bring down the material for the marl. 
To secure our lake from the encroachment of the sea, we 
require higher land to encircle it. Of this land we have some 
trace left in Wirral, and more in the Beeston, Helsby, and 
Overton Hills; while to attest that it was land, we have, in the 
places mentioned, foot-prints of Labyrinthodon, plant remains, 
sun-cracks, and possibly rain-pits. We have here all the machi- 
nery for the production of rock-salt, down even to the sun; the 
effect of whose rays are still visible in the cracked and shrivelled 
appearance of the so-called ‘“ water-stones.” 
It is obvious that, in the first instance, when the sandy barrier 
shut out the ocean from the little Cheshire lake, it would enclose 
a body of sea-water of considerable expanse, and as we have seen, 
2000 feet in depth probably. 
This body of water would undergo evaporation summer by 
summer, and as the loss in this way was greater than any inflow, 
it was only a question of time before the waters became brine, 
and from brine, salt. Before, however, this could be accom- 
plished, and as the waters lessened in bulk, they would naturally 
retreat to the lowest levels, which happened to be along the 
present valley of the Weaver, where we now find the greatest 
thickness of salt. deposits. 
We have rather anticipated in our sketch, for salt would be 
almost the last thing deposited from the waters of the lake. 
Not until more than ;4,ths of the water had evaporated would one 
grain of salt be deposited, and only when the lake had diminished 
from its former noble proportions to less than ;),th of original 
size and volume, would the salt separate. 
While all this had been going on, we may believe that the 
river, to which we made allusion, had not been inactive. Its 
