20 ORIGIN OF ROCK-SALT. 
muddy waters from the far north would come down laden with 
alluvial matters into our salt-lake, and in contact with its saline 
water would soon deposit. This would commence from the first 
inrush of its waters into the lake, and would continue to fall as 
long as the waters flowed in. This deposit we now call the 
Keuper Marl, and it forms the bed on which lies the rock-salt. 
Judging from the thickness of this marl deposit, it must have 
occupied a considerable period in formation. 
As a matter of fact the order of deposition would be marl and 
oxide of iron, as a first deposit; then carbonate of lime if present; 
and, when three-fourths of the water had been dissipated, the 
sulphate of lime or gypsum would form itself into a solid mass. 
A long pause would now ensue; the waters would continue to 
docrease until but a remnant remained, and the salt commenced 
to settle at the bottom of the lake. Now each particle of 
water evaporated means the settling down of a fragment of 
salt ; so that the result of a summer’s evaporation of the water 
would be the accumulation of a thickness of salt, such as we do 
not often mect with in other formations. Many feet of salt 
would be the result of a summer’s operation. 
I have thus briefly sketched the course of events which one 
may justly believe to have been the origin of the rock-salt of 
Cheshire. 
We may also now understand why it is that the deposit of 
rock-salt occupies a very limited area, since, as we have seen, it 
is only when a lake diminishes to the size of a large pool 
that the salt in it deposits. 
This is not the end of these salt deposits, for in looking at a 
section map of the district, we notice that a bed of marl caps the 
rock-salt as well as underlies it. How is this to be accounted 
for? Some geologists will tell us that the land was sinking, and, 
to fit in with their theory, in the same ratio as the marl and salt 
wore deposited. My own conviction is that nothing of the kind 
’ which I consider 
to have been impossible. Well then, you ask how do I account 
for this second bed of marl overlying the salt? A very fair 
occurred. It isa kind of geological “‘see-saw’ 
