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XVI. An Account of large fubterraneous Ca- 
verns in the Chalk Hills near Norwich ; by 
Mr . Wm. Arderon, F.R.S. comprifed in 
a Letter from Mr . Henry Baker F* R. S. 
to the Prefident. 
Read. March 24. \ S the Infpe&ion and Study of Na- 
j 747*8. ture i s the particular Province of 
the Royal Society, and every Attempt to improve 
our Knowledge is certain of your Favour, I take the 
Liberty to lay before you the Subftance of a Letter 
from my induftrious Correfpondent and Friend Mr. 
William Arderon , F. R. S. containing the Defec- 
tion of a large Vault or Cavern, extended under fe- 
veral Hills near the City of Norwich , with fome 
Obfervations and Experiments made by him there. 
About a Quarter of a Mile from the City of Nor- 
wich, on the Eaft Side thereof, and near the Entrance 
of Moujhold- Heath , is a large fubterraneous Cavern, 
which has been formed in a long Series of Time, 
by the digging out of Chalk for the making of Lime. 
There's but one Entrance into it, whofe Breadth is 
about two Yards, and its Height nearly the fame j 
however the Height gradually rifes, till at laft it 
meafures in fome Places from twelve to fourteen 
Yards. But notwithftanding the Entrance is fo fmall, 
the whole Area within is of fuch a large Extent, 
that twenty thoufand Men might with great Eafe be 
plac’d therein, as I believe will fcarcely be doubted, 
when I alfure you, that, from the Entrance to the 
furtheft Part of thefe darkfome Cells, meafures full 
four hundred Yards; and that thefe Paflages are fre- 
quently ten or twelve Yards wide, with Branchings 
