spreading inside the building, and developing with sufficient
intensity to work injury.

As it is of interest to the roofer to know the manner of making the
material he uses, we give in the following a short description of the
manufacture of roofing paper. At first, when square sheets were used
exclusively, the raw paper consisted of ordinary dipped or formed
sheets. The materials used in its manufacture were common woolen rags
and other material. In order to prepare the pulp from the rags it is
necessary to cut them so small that the fabric is entirely dissolved
and converted into short fibers. The rags are for this purpose first
cut into pieces, which are again reduced by special machines. The rags
are cut in a rag cutting machine, which was formerly constructed
similar to a feed cutter; later on, more complicated machines of
various constructions were employed. It is not our task to describe
the various kinds, but we remain content with the general remark that
they are all based on the principles of causing revolving knives to
operate upon the rags. The careful cleansing of the cut rags,
necessary for the manufacture of paper, is not required for roofing
paper. It is sufficient to rinse away the sand and other solid
extraneous matter. The further reduction of the cut rags was formerly
performed in a stamp mill, which is no longer employed, the pulp mill
or rag engine being universally used.

The construction of this engine may be described as follows: A box or
trough of wood, iron, or stone is by a partition divided into two
parts which are connected at their ends. At one side upon the bottom
of the box lies an oakwood block, called the back fall. In a hollow of
this back fall is sunk the so-called plate, furnished with a number of
sharp steel cutters or knives, lying alongside of each other. A roller