of the tar paper roof by a spark or flame from the outside was considered, and, second, it was tested in how far it would resist a fire in the interior of the building.  In the former case, it was ascertained that a bright, intense fire could be kept burning upon the roof for some time, without igniting the woodwork of the roof, but heat from above caused some of the more volatile constituents of the tar to be expelled, whereby small flames appeared upon the surface within the limits of the fire; the roofing paper was not completely destroyed.  There always remained a cohesive substance, although it was charred and friable, which by reason of its bad conductivity of heat protected the roof boarding to such an extent that it was “browned” only by the developed tar vapors.  A fire was next started within a building covered with a tar paper roof; the flame touched the roof boarding, which partly commenced to char and smoulder, but the bright burning of the wood was prevented by the air-tight condition of the roof; the fire gases could not escape from the building.  The smoke collecting under the roof prevented the entrance of fresh air, in consequence of which the want of oxygen smothered the fire.  The roofing paper remained unchanged.  By making openings in the sides of the building so that the fire gases could escape, the wood part of the roof was consumed, but the roofing paper itself was only charred and did not burn.  After removing the fire in contact with the paper, this ceased burning at once and evinced no disposition whatever to spread.  In large conflagrations, also, the tar paper roofs behaved in identically a similar manner.  Many instances have occurred where the tar paper roof prevented the fire from 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.