Work began on extending the canal westward from Lowtown in 1789. The company had already
experienced problems with a section of bog on the Barrow Line at Ballyteague and there had
been some discussion of how to tackle the Bog of Allen. William Chapman had suggested to the
directors that it was important to have the level of the canal sufficiently below the surface to
allow for subsidence, which was completely opposite to the views expressed some years earlier
by John Smeaton, who was acting as consultant engineer to the company at the time. He had
recommended: “Avoid a bog if you can, but by all means possible, the going deep into it”. In
other words he said the canal should be driven through the bog at the existing level.
Smeaton’s advice was followed and it fell to his pupil, William Jessop, who took over as
consultant engineer to the company, to oversee the work. No centre channel was dug out
initially but two parallel drains on either
side, leaving a centre pyramidal core to
be taken out as drainage occurred.
Transverse drains were also opened
up gradually. What Chapman had
predicted happened: the water drained
from the bog into the channels, which
subsided on either side of the line of
the canal and, with the surface of the
water in the canal at the original level
of the bog, they were left with large
unstable embankments. Travelling
across this part of the canal today, you
can observe the original level of the
canal some distance away, with the
subsided area in between on either
side of the canal.
When these first canals were built it was done with human endeavour, being prior to any mechanical steam assistance. The work was mainly undertaken by small private companies, an amalgamation being Henry, Mullins and McMahon (1808). Some perspective on the manpower required is taken from the 1790 workforce of 3,944 men on the Grand canal alone. (Figure taken from 'Industrial Ireland 1750-1930' by Colin Rynne).
If anyone has information in regard of this valuable part of our heritage feel free to add it.