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allowed to flow over tlie land, we were astonished day by day to 
find the fields to be soon covered witb circular boles, usually 
about 3, 4, or 5 feet in diameter and of various depths, the sides 
always being vertical/ &c. Mr. Morant attributes these sub- 
sidences to the excessive quantity of carbonated water suddenly 
poured over the land, and its effects on the numerous sandpipes 
which exist in the Chalk of that neighbourhood. On visiting 
the Whitlingham sewage farm at the end of last March, I saw 
many of these holes. Those I saw were seldom more than 2 or 
3 feet deep, hut I was told by the old man who was then en- 
gaged in distributing the sewage over the surface, that they 
often on first appearance were 10 or 12 feet deep, or even more, 
hut that they speedily filled themselves up, to the depth of those 
I saw, by the tumbling in of their sides. They are certainly 
very singular and worthy of notice, and are doubtless due to the 
cause assigned by Mr. Morant. But at Whitlingham we have 
an immense quantity of carbonated water making its way 
through loose, highly porous, sandy and gravelly beds, having a 
thickness of perhaps from 10 to 30 feet, to highly disturbed and 
probably fissured chalk below.* Another thing which seems to 
have had, in all probability, a special influence on the produc- 
tion of subsidences at Whitlingham is this. Among the strata 
overlying the Chalk, there is a bed of pebbles cemented together 
by oxide of iron and manganese, known locally as 4 iron- pan/ 
Where a sandpipe occurred in the Chalk below, the superior 
hardness and tenacity of the iron-pan would often be the 
means of preserving it unbroken and horizontal, while the 
softer and looser beds beneath the pan had adapted themselves 
to the shape taken by the sandpipe. A hollow space, shaped like 
an inverted cone, would be accordingly here and there formed 
beneath the iron-pan. The form taken by the subsidences at 
Whitlingham seems to me, therefore, to ha.ve been the result 
of the shape of the hollows probably existing below the pan, j 
which became suddenly filled up by the disintegration of the 
pan through the influx of sewage water. The anticlinal existing ] 
in the Chalk at Whitlingham may very probably reduce the 
maximum thickness of the overlying beds at the sewage farm 
to 20 feet or less. But, at all events, the differences between 
the Blackheath and Whitlingham subsidences must be suffi- 
ciently obvious. This Whitlingham case seemed to me, how- 
ever, well worth examination here, because it is the only one I 
have met with at all resembling that of Blackheath, which is 
best explained by the geological theory. 
We now come to the archaeological theory of the production 
of the Blackheath subsidences ; and perhaps the best plan will 
* See Reports of Papers by Dr. J. E. Taylor, on the ‘ Beds at Whit- 
lingham/ Geol. Mag. for 1865 (vol. ii.), pp. 324 and 370. 
