Again, springs are frequently active during seasons of drought, as 
the interval of time between the original rain-tall and the drought 
has becm occupied in percolating through the strata. Of all the 
Norfolk Meres, that at iJiss is the most remarkable. It is very 
deep in .some places, over twenty feet, and mu.st have been deeper 
originally, as the water poured into it has undoubtedly helped to 
fill it up by the deposition of sedimentary matter. There can be 
little doubt that the formation of Diss ^lere is due to glacial action, 
which has cut down all the overlying beds into the solid chalk, and 
left there the present remarkable b;isiu-shaped depression. The 
entire neighbourhood of Di.ss has been subjected to peculiar glacial 
action, as may bo seen in the ploughed-ont and contorted drift 
b(!(is, and I regard the hollow in which the Mere lies, a.s one among 
these phenomena. M ith the excej)tion of being ent down to the 
chalk, JJiss Mere in all re.spects answ(‘rs to the rule laid down. 
Scoulton Mere is easier to understand. Its waters are shallow, and 
ve know that time was when a greater area of the district was a 
s\\am])y marsh, not unlike the island which now occu]>ies the 
centre ot the j\lere. Cultivation has gradually contracted this area, 
until all that remains of it is the present state of thing.s. The 
Mere is situated on an e.xtensive and continuous sheet of ])oulder 
clay, on which rest several natural lakes of greater or le.ss size. 
At lower levels, in the Fen districts, wo have ^leres, as, for 
instance, the well-known one at hittlesea, now drained. These 
lie on the Kimnieridge clay— a formation considerably older than 
our chalk— which crops up beneath the Fen.s. It is quite as 
impervious to percolation as our own boulder clays, and thus pro- 
duces similar physical resemblances. The Fen district owes its 
swampiness to the underlay of this particular stratum, and the 
prevalence of the termination of its village and town names of 
“ea,” and “ey” — the Saxon words for island — indicate to us the 
condition of things a thousand years ago. 
INIeres are also common to Cheshire, where they usually lie over 
that formation termed the heupor. It is in this that the thick beds 
of rock-salt occur. I hat salt is being gradually dissolved away liy 
I)ercolating water, which issues to the surface as brine springs. 
Hence the overlying rock.s, in many places, aiv depressed, and then 
form hollows into which the superHcial water drains, and forms the 
well-known Cheshire Alert's. 
