advantage connected with this method. The surface of the paper as it
issues from the squeezing rollers is still very hot, and a part of the
volatile oils evaporate very quickly at this high temperature. The
surface is thereby at once dried to a certain degree and at the same
time receives a handsome luster, as if it had been coated with a black
lacquer. The paper is sanded in a very simple manner without the use
of mechanical apparatus; as it is being wrapped into a coil, it passes
with its lower surface over a layer of sand, while the workman who
tends to rolling up strews the inside with sand. The lower surface is
coated very equally. Care only being necessary that the sand lies
smooth and even at all times. When the workman has rolled up ten or
fifteen yards, he cuts it across with a knife and straightedge, so
that the paper is cut at right angles with its sides.

There are three different sorts of roofing paper, according to the
impregnating fluid used in its manufacture. The ordinary tar paper is
that saturated with clear cold tar. This contains the greatest amount
of fluid ingredients and is very raggy in a fresh condition. It is
easy to see that the volatile hydrocarbons evaporate in a short time,
and when expelled, the paper becomes stiffer and apparently drier.
This drying, or the volatilization of the hydrocarbons, causes pores
between the fibers of the paper. These pores are highly injurious to
it, as they facilitate a process of decomposition which will ruin it
in a short time.

Roofing paper can be called good only when it is essentially made from
woolen rags, and contains either very few or no earthy additions. It
is beyond doubt that the durability of a roofing paper increases with
the quality of wool fiber it contains--vegetable fibers and earthy
additions cause a direct injury. Reprehensible altogether is any