Mr Marr, The Meres of Breckland. 59 
of the water usually lies at from 15 to 25 feet below the rim. 
The floors are flat, and the waters shallow. 
They differ in size and shape, the smaller being most regular 
and approaching a circular outline: such are the Devil’s Punch 
Bowl, Ringmere and many nameless ponds, the latter often only 
a few feet in diameter. The largest are less than half a mile in 
length. These are irregular, often having sinuous shore-lines, 
and in some, as Langmere, one diameter is longer than the 
other. 
The meres in Wretham Park have undergone considerable 
modification at the hands of man, but those on the open heath 
are in their natural condition. 
Associated with the named meres are the above-mentioned 
small ponds. These grade downward in size to ordinary swallow- 
holes, such as occur in most limestone districts, and there is little 
doubt that these swallow-holes mark the starting-point in the 
formation of the larger meres. They are situated in chalk and, 
as in the ease of the meres which still hold water at times, near 
the junction of the chalk with overlying glacial deposits. 
Langmere and Ringmere lie in two tributary-valleys south of 
the plateau. Tracing these valleys downward to their coalescence 
near Roudham Junction, we find remains of similar hollows, now 
nearly always dry, and with the sides sloping gently to the 
floors. 
That the valleys existed before the meres is indicated by a 
deposit of river gravel exposed on the bank of Ringmere. 
The origin of some of the meres is probably complex. The 
swallow-holes may have begun as sand-pipes, as suggested by 
Mr Bennett, or, like those of other limestone regions, may be 
simply due to enlargement of a place on a joint by acidulated 
water, or to subsidence of part of the roof of a subterranean 
hollow. Such a subsidence giving rise to a pit at Rockland is 
described by Mr Bennett (loc. cit. p. 21). 
When sufficiently large, the surface-drainage of the little 
valleys situated on the glacial clays would, when reaching the 
chalk as it was exposed by the denudation of those clays, be 
carried underground through swallow-holes, but the transport of 
glacial clay to the floor of the swallow-hole might block it to a 
degree sufficient to prevent free drainage into the subterranean 
water-course, and hence the water would stand in the swallow- 
hole during wet periods. The standing water would sap the sides 
of the hole by solution, as suggested by Mr Bennett, slipping of 
the slope above would take place, as can now be seen in progress, 
and the hole would grow in circumference, giving rise ultimately 
to meres like the Punch Bowl and Ringmere. Coalescence of 
two or more would produce irregular meres like Langmere and 
