1. In Philadelphia, and in many other cities not only in this country,
but also in Europe, the stone-cutters _set their own work_; and this
practice has led to the habit of applying the term stone-mason to
both stone-cutters and those who lay stone in mortar and cement. In
New-York, however, as well as in some of the cities farther east,
these two employments are kept more distinct. The stone-cutters in
Philadelphia are sometimes denominated marble-masons.
2. But, in every city, there are persons called stone-masons, whose
business consists exclusively in constructing the walls and some other
parts of buildings with stone; and their operations are considerably
enlarged in those places where there are no marble-masons. In many
cases, the bricklayer is also so far a stone-mason, as to lay the
foundation-walls of the buildings which he may erect. This is
especially the case in the country, where the divisions of labor are
not so minute as in cities. It may be well here to remark, also, that
the bricklayers, in some places, perform the services of the
marble-mason.
3. The marble-mason, in joining together several pieces in a monument,
employs a kind of cement composed of about six parts of lime, one of
pure sand, a little plaster, and as much water as may be necessary to
form it to the proper consistency. No more of this cement is used than
is required to hold the blocks or parts together, as one great object
of the artist is to hide the joints as much as possible. The substance
thus interposed, becomes as hard as the marble itself.
4. The cement employed in laying marble in common or large edifices,
is somewhat different from that just described, as it consists of
about three fourths of lime and one of sand. The latter substance is
obtained, in an unmixed state, on the bays in every part of the world;
hence it has received the appellation of _bay sand_.
5. When it cannot be conveniently had in a pure state, particles of
the same kind can be separated in sufficient quantities from their
admixture with other substances. This is effected by sifting the
compound through a sieve, into a small stream of water, which carries
off the lighter particles that are unfit for use, whilst the sand, by
its superior specific gravity, sinks to the bottom. The part which may
be too coarse, remains in the sieve. This, however, except the
rubbish, can be used in the coarser kinds of masonry.
6. The mortar, used in laying bricks and common stone, has a greater
proportion of sand, which is generally of an inferior quality.
Besides, the materials are incorporated with less care. Lime for the
purposes of building is procured chiefly by calcining limestone in a
kiln, with wood, coal, or some other combustible substance. It is also
obtained by burning chalk, marble, and marine shells. Water poured
upon newly-burnt or _quick_ lime, causes it to swell, and fall to
pieces into a fine powder. In this state it is said to be _slacked_.
7. Masonry is often required in situations under water, especially in
the construction of bridges and locks of canals. Common mortar resists
the action of the water very well, when it has become perfectly dry;
yet, if it is immersed before it has had time to harden, it dissolves,
and crumbles away.
8. The ancient Romans, who practised building in the water to a great
extent, discovered a material, which, when incorporated with lime,
either with or without sand, possessed the property of hardening in a
few minutes even under water. This was a kind of earth found at
Puteoli, to which was given the name of _pulvis puteolanus_, and which
is the same now called _puzzolana_.
9. A substance denominated _tarras_, _terras_, or _tras_, found near
Andernach, in the vicinity of the Rhine, possesses the same quality
with puzzolana. It is this material which has been principally
employed by the Dutch, whose aquatic structures are superior to those
of any other nation in Europe. Various other substances, such as baked
clay and calcined greenstone, reduced to powder, afford a tolerable
material for water-cements. Several quarries of water lime, which is
similar in appearance to common limestone, has been lately discovered
in the United States, which, being finely pulverized and mixed with
sand, makes very good water-cement.
10. In buildings constructed with marble and other costly stones, the
walls are not composed of these materials in their entire thickness;
but, for the sake of cheapness, they are formed on the inside with
bricks, commonly of a poor quality, so that in reality they can be
considered only brick walls faced with stone. These two kinds of
materials have no other connexion than what is produced by the mortar
which may have been interposed, and the occasional use of clamps of
iron. Such walls are said to be liable to become convex outwardly from
the difference in the shrinking of the cement employed in laying the
two walls.
11. The principal tools employed in cutting and laying stone are the
saw, various kinds of steel points, chisels and hammers, the mallet,
the square, the compasses, the level, the plumb-rule, the trowel, and
the hod, to which may be added, the spade and the hoe. The last three
instruments, however, are handled almost exclusively by laborers.
12. Besides these, contrivances are required to raise heavy materials
to the various positions which they are to occupy. These consist, for
the most part, of one or two shafts, commonly the mast of an old
vessel, to which are attached tackle extending in various directions,
and also those by which the blocks are to be raised. The rope
belonging to the hoisting tackle is pulled by a machine worked with a
crank.
13. Masonry is one of the primitive arts, and was carried to great
perfection in ancient times. The pyramids of Egypt are supposed to
have stood about three thousand years, and they will probably remain
for centuries to come, monuments as well of the folly as of the power
and industry of man. The temples and other magnificent structures of
Greece and Rome, exhibit wonderful skill in masonry, and leave but
little, if anything new, to be achieved in modern times.