lue or black mortar contains equal
parts of foundry ashes and lime; but is improved by the addition of a
proportion of cement. For setting fire-bricks fire-clay is always used.
Pargetting for rendering inside chimney flues is made of one part of lime
with three parts of cow dung free from straw or litter. No efficient
substitute has been found for this mixture, which should be used fresh. A
mortar that has found approval for tall chimney shafts is composed by
grinding in a mortar-mill one part of blue lias lime with one part each of
sand and foundry ashes. In the external walls of the Albert Hall the mortar
used was one part Portland cement, one part grey Burham lime and six parts
pit sand. The lime was slaked twenty-four hours, and after being mixed
[v.04 p.0524] with the sand for ten minutes the cement was added and the
whole ground for one minute; the stuff was prepared in quantities only
sufficient for immediate use. The by-laws dated 1891, made by the London
County Council under section 16 of the Metropolis Management and Building
Acts Amendment Act 1878, require the proportions of lime mortar to be one
to three of sand or grit, and for cement mortar one to four. Clean soft
water only should be used for the purpose of making mortar.

_Grout_ is thin liquid mortar, and is legitimately used in gauged arches
and other work when fine joints are desired. In ordinary work it is
sometimes used every four or five courses to fill up any spaces that may
have been inadvertently left between the bricks. This at the best is but
doing with grout what should be done with mortar in the operation of laying
the bricks; and filling or flushing up every course with mortar requires
but little additional exertion and is far preferable. The use of grout is,
therefore, a sign of inefficient workmanship, and should not be
countenanced in good work. It is liable, moreover, to ooze out and stain
the face of the brickwork.

_Lime putty_ is pure slaked lime. It is prepared or "run," as it is termed,
in a wooden tub or bin, and should be made as long a time as possible
before being used; at least three weeks should elapse between preparation
and use.

[Illustration: FIG. 3.--Forms of Joints.]

The pointing of a wall, as previously mentioned, is done either with the
bricklaying or at the completion of the work. If the [Sidenote: Pointing.]
pointing is to be of the same mortar as the rest of the work, it would
probably greatly facilitate matte