small compared to the mass of the work, and the tenacity or hold upon
them of even fairly good lime mortar is so comparatively slight, that
there is really but little grip of one put upon another.

Persons who have to design and construct brick buildings should never
forget that they have to be handled with caution, and are really very
ticklish and unstable. One or two of the methods of overcoming this to
some extent may be mentioned. The first is the introduction of what is
called bond. At the end of the last century it was usual to build in, at
every few feet in height, bond timbers, which were embedded in the heart
of the walls. If these had always remained indestructible, they would no
doubt have served their purpose to some extent. Unfortunately, timber
both rots and burns, and this bond timber has brought down many a wall
owing to its being destroyed by fire, and has in other cases decayed
away, and caused cracks, settlements, and failures.

The more modern method of introducing a strong horizontal tie is to
build into the wall a group of bands of thin iron, such as some sorts of
barrels are hooped with--hence called hoop iron. The courses of bricks
where this occurs must be laid in cement, because iron in contact with
cement does not perish as it does in contact with mortar.

If in every story of a building four or five courses are thus laid and
fortified, a great deal of strength is given to the structure. Another
method, which has rather fallen into disuse, is grouting. This is
pouring liquid mortar, about the consistency of gruel, upon the work at
about every fourth course. The result is to fill up all interstices and
cavities, and to delay the drying of the mortar, and brickwork so
treated sets extremely hard. I have seen a wall that had been so treated
cut into, and it was quite as easy to cut the bricks (sound ones though