couple
of thin wedges were driven very moderately at the butt-end of the
stone; whose tendency being to force it out of its dove-tail, they
would, by moderate driving, only tend to preserve the whole mass
steady together, in opposition to the violent agitation that might
arise from the sea.' In addition to this, a couple of holes having
been bored through every piece of stone, one course was bound to
another by oak trenails driven stiffly through, and made so fast that
they could more easily be torn asunder than pulled out again. 'No
assignable power,' says Smeaton, 'less than what would by main stress
pull these trenails in two could lift one of these stones from their
beds when so fixed, exclusive of their natural weight, as all
agitation was prevented by the lateral wedges.' The stone being thus
fixed, a proper quantity of mortar was liquefied; and the joints
having been carefully pointed, up to the upper surface, this mortar or
cement was poured in with iron ladles so as to occupy every void
space. The more consistent parts of this cement naturally settled to
the bottom, and the watery parts were absorbed by the stone: the
vacancy thus left at the top was repeatedly refilled, until all
remained solid; the top was then pointed, and, when necessary,
defended by a coat of plaster. When the whole of the foundation was in
this manner brought to a level, some other means was necessary of
attaining the like degree of security. For this purpose the central
stone of the sixth course had a hole of one foot square cut quite
through the middle. Eight other depressions of one foot square and six
inches deep were also sunk at equal distances in the circumference. A
plug of strong hard marble, from the rocks near Plymouth, one foot
square and twenty-two inches in length, was set with mortar in the
central cavity, and fixed firmly therein with their wedges. This
course was thirteen inches in height, so that the marble plug, which
reached through it, stood nine inches above the surface. Upon this the
centre-stone of the seventh course was fixed, having a similar hole
made in its centre, bedded with mortar and wedged as before. By this
means no force of the sea acting horizontally upon the centre-stone,
less than what was capable of cutting the marble plug in two, was able
to move it from its place; and to prevent the stone the more
effectually from being lifted, in case its bed of mortar should happen
to be destroyed, it was fixed d