weakest material--i.e., the mortar--though when it is in cement the
strength of brickwork to withstand a weight probably approaches that of
the individual bricks. Some experiments quoted in Rivington's Notes give
the following as the crushing weight per foot--that is to say, weight at
which crushing began--of piers having a height of less than twelve times
their diameter:

Tons per
foot.
Best stocks, set in Portland cement and
sand 1 to 1, and three months old. 40
Ordinary good stocks, three months old. 30
Hard stocks, Roman cement and sand 1 to 1,
three months old. 28
Hard stocks, lias lime, and sand 1 to 2,
and six months old. 24
Hard stocks, gray chalk lime, and sand,
six months old. 12

The rule given in popular handbook, that brickwork in mortar should not
have to carry more than three tons per superficial foot, and in cement
more than five tons, is probably sound, as in no building ought the load
to approach the crushing point, and, indeed, there are many sorts of
foundations on which such a load as five tons per foot would be too
great to be advisable.

It is a rather interesting inquiry, whenever we are dealing with a
building material, if we ask what can we best do with it, and for what
is it ill fitted. The purposes for which brick can be best used depend,
of course, upon its qualities. Speaking generally, such purposes are