-five
feet, but its greatest breadth, as seen at low-water of spring-tides,
is only twenty-three feet; hence it was not possible to obtain a base
for a building of greater diameter than eighteen feet. The surface of
the rock was also so rugged that it was necessary to excavate part of
the foundation-pit of the building to the depth of seven feet. The
difficulties were still further increased on account of the foundation
being partly under the level of the lowest tides, so that a coffer-dam
was required. It was further necessary, after each tide's work, to
remove and carry ashore part of this coffer-dam; so that on the return
of the workmen at ebb-tide much time was lost in readjusting the
coffer-dam, and in pumping the water out of the foundation-pit.

Some idea may be formed of the difficulties attending the early stages
of this work, from the fact that during the whole of the first season,
or summer of 1813, the workmen could not command more than forty-one
hours' work upon the rock; during the second season the time was only
fifty-three hours. These two years were entirely occupied in
excavating and preparing the foundation, and in laying ten stones, or
the half course of masonry, which brought the foundation to a uniform
level for the first entire course of the building. Mr. Stevenson
contrasts this slow progress with that made at the Bell Rock during
the first two seasons. Although this building was situated twelve
miles from the shore, three courses were erected, the diameter of the
base being forty-two feet, besides the erection of a beacon-house or
barrack for the workmen. 'The establishment for the works at the Bell
Rock was of course on a much larger scale than that of the Carr Rock;
but still the latter was equally effective, and the same apparatus,
artificers, and seamen, were employed at both.'

During the third year's work, the second course of the masonry was
completed upon the Carr; and nine stones of the third course were laid
by the 3rd of October, when a heavy ground-swell obliged the workmen
precipitately to leave the rock and take to their boats. Before the
cement was fixed, the surge of the sea had washed it out; the oaken
trenails were wrenched off, and the whole of the nine blocks of stone
swept off the rock and lost in deep water, though they had been
completely dove-tailed and fitted on the same principles as the
masonry of the Bell-Rock lighthouse, where not a single stone was lost
during th