in churches where the width
of the bays of the aisles was calculated, they were much more likely to
take place where builders worked with less accurate ideas of
measurement. In an unvaulted church, where the pressure of the roof is
not a serious factor in the construction, the exact correspondence of
pier to buttress need not be taken into account; and there are many
churches in which the spacing of the aisles is quite independent of that
of the arcades. This happens at Melbourne, where the church was not
planned for stone vaulting. The builders seem to have thought that they
could get in six bays between the transept and the space planned for
one of the western towers; but found that, on the measurements they had
adopted, there was room only for five. They corrected their
miscalculation by broadening the division of the wall between the fourth
and fifth bay of the aisles. When they came to build the arcades, they
were conscious of their previous error, and planned them in five equal
bays irrespective of the plan of the aisles. In churches of the
fourteenth and fifteenth centuries, especially in districts like Norfolk
or south Lincolnshire, where much rebuilding was done, the regularity of
plan is often remarkable. The nave of the famous church of Heckington,
near Sleaford, was planned with an exact correspondence between aisles
and arcades: pier is opposite buttress, window opposite window. Islip
and Brampton Ash in Northamptonshire show an equal accuracy. But, while
such agreement is desirable, it is neither necessary nor general. And,
where the arcades are broken through earlier walls, the correspondence
is seldom very precise. The central line of the east walls of the
aisles, as set out first, will usually correspond to a line drawn across
the centre of the chancel arch: similarly, the line of the west walls
will be an extension of the west wall of the nave, or of a line drawn
across the tower arch. The aisles will be spaced into as many equal, or
nearly equal bays, as can be got in between the buttresses at either
end. When, however, the building of the arcade is taken in hand, the
responds or half-piers at either end will seldom be built directly
against the piers of the chancel arch, or against the west wall of the
nave; but projecting pieces of the old walls will be left as a backing
to them. It follows that, although the arcade may be divided into the
same number of bays as the aisles, the standard of spacing wi