A. O. G. Cameron—Hertfordshire Subsidences. 25 
find a windlass and bucket erected over a circular hole or shaft sunk 
deep in the Chalk, while a man at the bottom, working right and left 
of him, sends bucketfuls of dazzling, white chalk to the surface, 
which is wheeled away in barrows, and deposited in heaps close to 
one another, in the field where the shaft has been sunk, to be after- 
wards broken up, and lain about the place. 
When all the chalk that is required has been dug up, the windlass 
disappears, and the hole is filled up to the original surface level, in 
order that no unnecessary unevenness should occur to mar the 
ploughing. Gradually however, a subsidence takes place, as the 
material, with which the hole was filled, settles down in the cavity 
prepared for it, and then for a time, a basin-shaped hollow marks the 
site of the shaft. Suddenly a deep ring-like orifice, the sides of 
which show a clear section of the earth and stones, with which the 
hole was filled, appears at the bottom of the pit, and a veritable 
swallow-hole is formed on the spot. 
If it is only a subsiding hole, that is, one that may go down at 
any moment, a short funnel or pipe is seen, without the ring-like 
orifice and clean cut sides. 
Harvest is the time, I am told, when these pits most frequently fall- 
in; but as the subsidences also occur during rainy seasons, when 
water wells up or accumulates at the bottom, I am inclined to think 
the reported falling in at harvest time is greatly accounted for by 
reason of more people being in the fields then to observe them than 
at any other time. Holes are being re-filled this autumn about here, 
that have required filling several times before. 
In some parts of the county “ doming” is resorted to for covering 
the holes, thereby obviating the periodical filling up, which may 
require doing yearly. A pit to be domed, is first nearly filled up 
to the original surface-level, at least presumably so—and then arched 
over with brickwork and covered with earth. This plan is said to 
cost no more than the other, but the latter is the safer of the two. 
A labourer informed me that somewhere in the Baldock country, 
a domed hole once caved in when a ploughman and lad with three 
horses were crossing it. The two attendants had a narrow escape 
for their lives, the three horses were killed. Poles are sometimes 
put up to show the sites of these pits. 
The foregoing brings to my recollection much that is in common 
with the ‘natural pits’ at Ripon,! where it will be remembered a 
haystack disappeared down a cavity” that suddenly opened in the 
limestone, during the time the haymakers had adjourned for dinner. 
Doubtless some Hertfordshire subsidences® are as natural as those at 
Ripon—due to the dissolution of the strata by acidulated waters. 
Semicireular holes in the chalk filled with brickearth, often seen 
1 See Natural Pits at Ripon, by Rev. Stanley Tute, Proc. Yorks. Geol. and Polyt. 
Soc. 1869. Also ‘Subsidences over Permian Limestone,’ A. C. G. Cameron, Rep. 
Brit. Assoc. York, 1881, and Proc. Yorks. Geol. and Polyt. Soc. vol. vii. pt. iv. 
2 Locally named ‘‘shoots’’ and “ earthquakes.”’ 
3 See ‘‘ Nature,’ vol. xxxvii. Dec. 8, 1887, On an Earthquake in England, 
by Worthington G. Smith. 
