Civil Engineering Reference
In-Depth Information
Quite contrary was the procedure of building other megalithic monuments
divorced from earth tumuli—the standing stones (menhirs) and stone circles
(cromlechs). Here it would have been practical procedure to heap up
ad hoc
construction ramps of earth and proceed in the manner outlined above. However
where the site is extensive and well dei ned (e.g. Stonehenge) there are indications
that this did not take place. No trace of mound building survives at the relev-
ent positions and (even more emphatically) there are no traces of the disposal
of the large masses of earth required (R.J.C. Atkinson,
Stonehenge
, p. 134; but cf
D. Souden,
Stonehenge
, p. 93).
Standing stones were set up in the following manner. h e sunken emplacement
for the foot was dug with one face inclined at a suitable angle to form a “slideway”.
h e “menhir” was brought base i rst up to the emplacement with the foot projecting
over the inclined cutting, the stone resting on timber rollers. h e far end (top) of
the menhir was then levered upwards and the stone slid down the inclined cutting
to rest at an angle at the bottom of the emplacement. It was then hauled vertical by
ropes attached to its head (perhaps with the interposition of shear legs to engineer
a more ef ective angle of traction) (R.J.C. Atkinson,
Stonehenge
, pp. 131-34).
Horizontal slabs (cap stones) were levered up to the necessary height (eg up to
ca 6 m). h is could only be done employing the device of “cribbing”. A heavy stone
slab can be raised up by repeated levering and wedging (chocking / packing) it
from below with e.g. wooden chocs. Since the fulcrum for applying the lever must
also be raised
pari passu
the packing soon becomes unstable and will not sui ce
for more than half a metre or so. h e process of cribbing then involves building
up beneath the raised block a platform or staging so that the levering process can
be repeated
ab initio
, and so on until the required height is attained. h is seems a
tall order, and so it is; but it is carried out with a profuse supply of long and heavy
baulks of timber which are laid down parallel at intervals and then another set
of baulks are laid across them at intervals. h en a plank l oor is laid to provide a
working platform. h e process is repeated until the raised staging is at the height
to lever the cap stone across into place (R.J.C. Atkinson,
Stonehenge
, pp. 134-39;
D. Souden,
Stonehenge
, pp. 92-93).
h e quantity of timbering required is enormous, but it is not i xed together in
any way and is assembled and dismantled without trouble. h us the one store of
timber serves for all occasions when cribbing is required.
In brief the erection of stones of great burden (at times ca 50 tons) was engi-
neered with ample supplies of earth, timber, ropes, grease and manpower. h e
marshalling of these resources on a construction site and their disposition for car-
rying out very heavy works involved notable development and installations. Some
idea of this is perhaps given by considering the rôle of the engineer in charge of
the operations.
Free
standing
stones
228
58, 59
