'lhs being accomplished, Mr.
Brunel b''g in his operation, a la teredo.
; He placed Lis great iron shell or shield
at the bottom ot bis well. This shield
consisted of twelve ca-t iron frames,
standing side by side like books on a
shelf, the. front towards the digging
covered with moveable planks, three
ti rs thick. A hole was made in the
Ini k cvilinder wall, and the shield,
about lo- \ fi et wide and twenty feet
high, w striven into the clay under
:l''f* 'Thar; The manner of working
| was this In each of the thirty-six co-
Ipartmenr- or gall lies of the frame, a
workman as placed, who removed
the plank and digging out the earth
for a foot or two bev ond it. which earth
'was thrown out backwards and imme
diately removed, placed the plank
!against the earth and secured it with
props. All the planks being thus
propped forward, the shield was mov
ed up to them by means of screws at
the top and bottom, one section n* a
t’me. Thisicll ved a section of the
tunnel for masonry behind, which was
immediately occupied by an arched
wall with support in the centre, form
ing a double carriage way. The wall
is enormously thick and strong, leaving
Carriage ways that are fifteen feet high
and wide enough lor one carriage at a
time and a narrow sidewalk for foot
passengers. There arc arches con
stantly communicating from one car
riage way to Ihe other. These are oc
cupied as stalls for the sale of nil man
ner of confectionary and haberdash
ery, being brilliantly lighted with ga®.
