ted upon a shaft at the back end of the pan,
and by suitable arrangement of guide rollers it unwinds slowly, passes
into the tar in which it is kept submerged. The guide rollers can be
raised so that when a new roller is set up they can be raised out of
the tar. The end of the paper is then slipped underneath them above
the surface of the tar, when having passed through the squeezing
rollers, it is fastened to the beaming roller, and the guide rollers
are submerged again. A workman slowly turns the crank of the beaming
roller.

This motion draws the paper slowly through the fluid, the roll at the
back end unwinding. The speed with which the squeezing rollers are
turned is regulated in such a manner that the paper remains
sufficiently long underneath the fluid to be thoroughly impregnated
with it. The workmen quickly learn by experience how fast to turn the
crank. The hotter the tar, the more rapid the saturation; the high
degree of heat expels the air and evaporates the hygroscopic fluid in
the pores of the paper. The strong heating of the tar causes another
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